,,american ,,society ,,of ,,civil       
,,engineers ,,instituted #aheb          
,,transactions  ,paper ,no4 #aagd       
,,pressure1 ,,resistance1 ,,and         
,,stability ,,of ,,earth4,a  ,,by ,j4,c4
 ,,meem1 ,m4 ,,am4 ,,soc4 ,c4 ,e4       
,,with ,,discussion ,,by ,,messrs4 ,t4  
,,kennard ,,thomson1 ,,charles ,e4      
,,gregory1 ,,francis ,w4 ,,perry1 ,e4,p4
 ,,goodrich1 ,,francis ,l4 ,,pruyn1     
,,frank ,h4 ,,carter1 ,,and ,j4,c4      
,,meem4   ,in the final discussion of   
the writer's paper1 ,the ,bracing of    
,trenches and ,tunnels1 ,with ,practical
 ,formulas for ,earth ,pressures1,b     
certain minor experiments were noted in 
connection with the arching properties  
of sand4 ,in the present paper it is    
proposed to take up again the question  
of earth pressures1 but in more detail1 
and to note some further experiments and
 deductions therefrom1 and also to      
consider the resistance and stability of
 earth as applied to piling and         
foundations1 and the pressure on and    

buoyancy of subaqueous structures in    
soft ground4  ,in order to make this    
paper complete in itself1 it will be    
necessary1 in some instances1 to include
 in substance some of the matter of the 
former paper1 and indulgence is asked   
from those readers who may note this    
fact4  ,illustration3 ,,fig4 #a4        
,,sections ,,of ,,box-,,frame ,,for     
,,sand-,,arch ,,experiment  ,experiment 
,no4 #a4--;,as the sand-box experiments 
described in the former paper were on a 
small scale1 exception might be taken to
 them1 and therefore the writer has made
 this experiment on a scale sufficiently
 large to be much more conclusive4 ,as  
shown in ,fig4 #a1 wooden abutments1 #c 
ft4 wide1 #c ft4 apart1 and about #a ft4
 high1 were built and filled solidly    
with sand4 ,wooden walls1 #c ft4 apart  
and #d ft4 high1 were then built        
crossing the abutments1 and solidly     
cleated and braced frames were placed   
across their ends about #b ft4 back of  
each abutment4 ,a false bottom1 made to 

slide freely up and down between the    
abutments1 and projecting slightly      
beyond the walls on each side1 was then 
blocked up snugly to the bottom edges of
 the sides1 thus obtaining a box #c by  
#d by #g ft41 the last dimension not    
being important4 ,bolts1 #dd in4 long1  
with long threads1 were run up through  
the false bottom and through #f by #ae  
by #b-;in4 pine washers to nuts on the  
top4 ,the box was filled with ordinary  
coarse sand from the trench1 the sand   
being compacted as thoroughly as        
possible4 ,the ends were tightened down 
on the washers1 which in turn bore on   
the compacted sand4 ,the blocking was   
then knocked out from under the false   
bottom1 and the following was noted3    
,as soon as the blocking was removed the
 bottom settled nearly #b in41 as noted 
in ,fig4 #a1 ,plate ,,xxiv1 due to the  
initial compacting of the sand under the
 arching stresses4 ,a measurement was   
taken from the bottom of the washers to 
the top of the false bottom1 and it was 

noted as #da in4 7,fig4 #a74 ,after some
 three or four hours1 as the arch had   
not been broken1 it was decided to test 
it under greater loading1 and four men  
were placed on it1 four others standing 
on the haunches1 as shown in ,fig4 #b1  
,plate ,,xxiv4 ,under this additional   
loading of about #fjj lb4 the bottom    
settled #b in4 more1 or nearly #d in4 in
 all1 due to the further compression of 
the sand arch4 ,about an hour after the 
superimposed load had been removed1 the 
writer jostled the box with his foot    
sufficiently to dislodge some of the    
exposed sand1 when the arch at once     
collapsed and the bottom fell to the    
ground4  ,referring to ,fig4 #b1 if1    
instead of being ordinary sand1 the     
block comprised within the area1 ,a ,u  
,j ,v ,x1 had been frozen sand1 there   
can be no reason to suppose that it     
would not have sustained itself1 forming
 a perfect arch1 with all material      
removed below the line1 ,v ,e ,j1 in    
fact1 the freezing process of tunneling 

in soft ground is based on this         
well-known principle4  ,illustration3   
,,fig4 #b4  ,illustration3 ,,fig4 #c4   
,if1 then1 instead of removing the mass1
 ,j ,e ,v1 it is allowed to remain and  
is supported from the mass above1 one   
must concede to this mass in its normal 
state the same arching properties it    
would have had if frozen1 excepting1 of 
course1 that a greater thickness of key 
should be allowed1 to offset a greater  
tendency to compression in moist and dry
 as against frozen sand1 where both are 
measured in a confined area4  ,if1 in   
,fig4 #b1 ,e ,v ,j  phi  the angle of   
repose1 and it be assumed that ,a ,j1   
the line bisecting the angle between    
that of repose and the perpendicular1   
measures at its intersection with the   
middle vertical 7,a1 ,fig4 #b7 the      
height which is necessary to give a     
sufficient thickness of key1 it may be  
concluded that this sand arch will be   
self-sustaining4 ,that is1 it is assumed
 that the arching effect is taken up    

virtually within the limits of the area1
 ,a ,n#a ,v ,e ,j ,n ,a1 thus relieving 
the structure below of the stresses due 
to the weight or thrust of any of the   
material above2 and that the portion of 
the material below ,v ,e ,j is probably 
dead weight on any structure underneath1
 and when sustained from below forms a  
natural centering for the natural arch  
above4 ,it is also probably true that   
the material in the areas1 ,x ,n#a ,a   
and ,a ,n ,u1 does not add to the       
arching strength1 more especially in    
those materials where cohesion may not  
be counted on as a factor4 ,this is     
borne out by the fact that1 in the      
experiment noted1 a well-defined crack  
developed on the surface of the sand at 
about the point ,u#a1 and extended      
apparently a considerable depth1 assumed
 to be at ,n1 where the haunch line is  
intersected by the slope line from ,a4  
,illustration3 ,,plate ,,xxiv1 ,,fig4   
#a4--;,,initial ,,settlement ,,in       
#c-;,,ft4 ,,sand ,,arch1 ,,due ,,to     

,,compression ,,of ,,material ,,on      
,,removing ,,supports ,,from ,,bottom4  
,illustration3 ,,plate ,,xxiv1 ,,fig4   
#b4--;,,final ,,settlement ,,of ,,sand  
,,arch1 ,,due ,,to ,,compression ,,in   
,,excess ,,loading4  ,in this experiment
 the sand was good and sharp1 containing
 some gravel1 and was taken directly    
from the adjoining excavation4 ,when    
thrown loosely in a heap1 it assumed an 
angle of repose of about #de degrees4   
,it should be noted that this material  
when tested was not compacted as much1  
nor did it possess the same cohesion1 as
 sand in its normal undisturbed         
condition in a bank1 and for this reason
 it is believed that the depth of key   
given here is absolutely safe for all   
except extraordinary conditions1 such as
 non-homogeneous material and others    
which may require special consideration4
  ,referring again to the area1 ,a ,n#a 
,v ,j ,n ,a1 ,fig4 #b1 it is probable   
that1 while self-sustaining1 some at    
least of the lower portion must derive  

its initial support from the centering  
below1 and the writer has made the      
arbitrary assumption that the lower half
 of it is carried by the structure while
 the upper half is entirely independent 
of it1 and1 in making this assumption1  
he believes he is adding a factor of    
safety thereto4 ,the area1 then1 which  
is assumed to be carried by an          
underground structure the depth of which
 is sufficient to allow the lines1 ,v ,a
 and ,j ,a1 to intersect below the      
surface1 is the lower half of ,a ,n#a ,v
 ,e ,j ,n ,a1 or its equivalent1 ,a ,v  
,e ,j ,a1 plus the area1 ,v ,e ,j1 or ,a
 ,v ,j ,a1 the angle1 ,a ,v ,j1 being   
#a                                   phi
 alpha  --- 7 #ij - phi 7  phi  #de     
-------4            #b                  
#b  ,it is not probable that these lines
 of thrust or pressure transmission1 ,a 
,n1 ,d ,k1 etc41 will be straight1 but1 
for purposes of calculation1 they will  
be assumed to be so2 also1 that they    
will act along and parallel to the lines

 of repose of their natural slope1 and  
that the thrust of the earth will       
therefore be measured by the relation   
between the radius and the tangent of   
this angle multiplied by the weight of  
material affected4 ,the dead weight on a
 plane1 ,v ,j1 due to the material      
above1 is1 therefore1 where      l  span
 or extreme width of opening  ,v ,j1    
,w  weight per cubic foot of material1  
and     ,w#a  weight per linear foot4   
#b  7l _/ #b7 tan4 alpha  ,w ,w#a       
----------------------------------      
#b      #a            _/ #a             
--- l tan4  --- 7#ij - phi7  phi  ,w    
#b             #b                       
_/       l                phi     ----- 
tan4 7 #de  ------- 7 ,w4       #b      
#b  ,the application of the above to    
flat-arched or circular tunnels is very 
simple1 except that the question of side
 thrust should be considered also as a  
factor4 ,the thrust against the side of 
a tunnel in dry sand having a flat angle
 of repose will necessarily be greater  

than in very moist sand or clay1 which  
stands at a much steeper angle1 and1 for
 the same reason1 the arch thrust is    
greater in dryer sand and therefore the 
load on a tunnel structure should not be
 as great1 the material being compact   
and excluding cohesion as a factor4     
,this can be illustrated by referring to
 ,fig4 #c in which it is seen that the  
flatter the position of the rakers      
keying at ,w#a1 ,w#b1 and ,w1 the       
greater will be the side thrust at ,a1  
,c1 and ,f4 ,it can also be illustrated 
by assuming that the arching material is
 composed of cubes of polished marble   
set one vertically above the other in   
close columns4 ,there would then be     
absolutely no side thrust1 but1         
likewise1 no arching properties would be
 developed1 and an indefinite height    
would probably be reached above the     
tunnel roof before friction enough would
 be developed to cause it to relieve the
 structure of any part of its load4     
,conversely1 if it be assumed that the  

superadjacent material is composed of   
large bowling balls1 interlocking with  
some degree of regularity1 it can be    
seen that those above will form         
themselves into an arch over the        
centering made up of those supported    
directly by the roof of the structure1  
thus relieving the structure of any load
 except that due to this centering4     
,if1 now1 the line1 ,a ,b1 in ,fig4 #d1 
be drawn so as to form with ,a ,c the   
angle1 beta1 to be noted later1 and it  
be assumed that it measures the area of 
pressure against ,a ,c1 and if the line1
 ,c ,f1 be drawn1 forming with ,c ,g1   
the angle1 alpha1 noted above1 then ,g  
,f can be reduced in some measure by    
reason of the increase of ,g ,c to ,c   
,b1 because the side thrust above the   
line1 ,b ,c1 has slightly diminished the
 loading above4 ,the writer makes the   
arbitrary assumption that this decrease 
in ,g ,f should equal #bj of ,b ,c  ,f  
,d#a4 ,if1 then1 the line1 ,b ,d#a be   
drawn1 it is conceded that all the      

material within the area1 ,a ,b ,d#a ,g 
,c ,a1 causes direct pressure against or
 upon the structure1 ,g ,c ,a1 the      
vertical lines being the ordinates of   
pressure due to weight1 and the         
horizontal lines 7qualified by certain  
ratios7 being the abscissas of pressure 
due to thrust4 ,an extreme measurement  
of this area of pressure is doubtless   
approximately more nearly a curve than  
the straight lines given1 and the curve1
 ,a ,r ,t ,i ,d,,ii1 is therefore drawn 
in to give graphically and approximately
 the safe area of which any vertical    
ordinate1 multiplied by the weight1     
gives the pressure on the roof at that  
point1 and any horizontal line1 or      
abscissa1 divided by the tangent of the 
angle of repose and multiplied by the   
weight per foot1 gives the pressure on  
the side at that point4  ,illustration3 
,,fig4 #d4  ,the practical conclusion of
 this whole assumption is that the      
material in the area1 ,f ,e ,c ,b ,b#a1 
forms with the equivalent opposite area 

an arch reacting against the face1 ,c ,b
 ,b#a and that1 as heretofore noted1 the
 lower half 7or its equivalent1 ,b ,d#a 
,g ,b7 of the weight of this is assumed 
to be carried by the structure1 the     
upper half being self-sustaining1 as    
shown by the line1 ,b,,iii ,d,,iv 7or1  
for absolute safety1 the curved line71  
and therefore1 if rods could be run from
 sheeting inside the tunnel area to a   
point outside the line1 ,f ,b#a1 as     
indicated by the lines1 #e1 #f1 #g1 #h1 
#aa1 #ab1 #ac1 etc41 that the internal  
bracing of this tunnel could be omitted1
 or that the tunnel itself would be     
relieved of all loading1 whereas these  
rods would be carrying some large       
portion at least of the weight within   
the area circumscribed by the curve1    
,d,,ii ,i ,t ,g1 and further1 that a    
tunnel structure of the approximate     
dimensions shown would carry its maximum
 load with the surface of the ground    
between ,d,,iv and ,f1 beyond which     
point the pressure would remain the same

 for all depths4  ,in calculating       
pressures on circular arches1 the arched
 area should first be graphically       
resolved into a rectangular equivalent1 
as in the right half of ,fig4 #d1       
proceeding subsequently as noted4  ,the 
following instances are given as partial
 evidence that in ordinary ground1 not  
submerged1 the pressures do not exceed  
in any instance those found by the above
 methods1 and it is very probable that  
similar instances or experiences have   
been met by every engineer engaged in   
soft-ground tunneling3  ,in building the
 ,bay ,ridge tunnel sewer1 in #fb;d and 
#fdth ,streets1 ,brooklyn1 the arch     
timber bracing shown in ,fig4 #a1 ,plate
 ,,xxvi1 was used for more than #d1jjj  
ft41 or for two-thirds of the whole     
#e1hjj ft4 called for in the contract4  
,the external width of opening1 measured
 at the wall-plate1 averaged about #ai  
ft4 for the #ad-;ft4 circular sewer and 
#ai ft4 for the #ae-;ft4 sewer4 ,the    
arch timber segments in the             

cross-section were #aj by #ab-;in4      
,north ,carolina pine of good grade1    
with #b in4 off the butt for a bearing  
to take up the thrust4 ,they were set #e
 ft4 apart on centers1 and rested on #f 
by #ab-;in4 wall-plates of the same     
material as noted above4 ,the ultimate  
strength of this material1 across the   
grain1 when dry and in good condition1  
as given by the ,united ,states         
,forestry ,department tests is about    
#a1jjj lb4 in compression4 ,some tests,c
 made in #aijg by ,mr4 ,e4,f4 ,sherman  
for the ,charles ,river ,dam in ,boston1
 ,mass41 show that in yellow pine1 which
 had been water-soaked for two years1   
checks began to open at from #chh to    
#eha lb4 per sq4 in41 and that yields of
  in4 were noted at from #fjj to #a1jjj 
lb4 ,as the tunnel wall-plates described
 in this paper were subject to          
occasional saturation1 and always to a  
moist atmosphere1 they could never have 
been considered as equal to dry         
material4 ,had the full loading shown by

 the foregoing come on these            
wall-plates1 they would have been       
subjected to a stress of about #be tons 
each1 or nearly one-half of their       
ultimate strength4 ,in only one or two  
instances1 covering stretches of #ajj   
ft4 in one case and #bjj ft4 in another1
 where there were large areas of        
quicksand sufficient to cause           
semi-aqueous pressure1 or pockets of the
 same material causing eccentric        
loading1 did these wall-plates show any 
signs of heavy pressure1 and in many    
instances they were in such good        
condition that they could be taken out  
and used a second and a third time4 ,two
 especially interesting instances came  
under the writer's observation3 ,in one 
case1 due to a collapse of the internal 
bracing1 the load of an entire section1 
#be ft4 long and #ai ft4 wide1 was      
carried for several hours on ribs spaced
 #e ft4 apart4 ,the minimum             
cross-section of these ribs was #gc sq4 
in41 and they were under a stress1 as   

noted above1 of #ej1jjj lb41 or nearly  
up to the actual limit of strength of   
the wall-plate where the rib bore on it4
 ,when these wall-plates were examined1 
after replacing the internal bracing1   
they did not appear to have been under  
any unusual stress4  ,illustration3     
,,plate ,,xxv1 ,,fig4 #a4--,,normal     
,,slopes ,,and ,,strata ,,of ,,newly    
,,excavated ,,banks4  ,illustration3    
,,plate ,,xxv1 ,,fig4 #b4--,,normal     
,,slopes ,,and ,,strata ,,of ,,newly    
,,excavated ,,banks4  ,in another       
instance1 for a distance of more than   
#gjj ft41 the sub-grade of the sewer was
 #d ft4 below the level of the water in 
sharp sand4 ,in excavating for bottoms  
the water had to be pumped at the rate  
of more than #cjj gal4 per min41 and it 
was necessary to close-sheet a trench   
between the wall-plates in which to     
place a section of bottom4 ,in spite of 
the utmost care1 some ground was        
necessarily lost1 and this was shown by 
the slight subsidence of the wall-plates

 and a loosening up of the wedges in the
 supports bearing on the arch timbers4  
,during this operation of bottoming1 two
 men on each side were constantly       
employed in tightening up wedges and    
shims above the arch timbers4 ,it is    
impossible to explain the fact that     
these timbers slackened 7without        
proportionate roof settlement7 by any   
other theory than that the arching was  
so nearly perfect that it relieved the  
bracing of a large part of the load1 the
 ordinary loose material being held in  
place by the arching or wedging together
 of the #b-;in4 by #c-;ft4 sheeting     
boards in the roof1 arranged in the form
 of a segmental arch4 ,the material     
above this roof was coarse1 sharp sand1 
through which it had been difficult to  
tunnel without losing ground1 and it had
 admitted water freely after each rain  
until the drainage of a neighboring pond
 had been completed1 the men never being
 willing to resume work until the influx
 of water had stopped4  ,the foregoing  

applies only to material ordinarily     
found under ground not subaqueous1 or   
which cannot be classed as aqueous or   
semi-aqueous material4 ,these conditions
 will be noted later4  ,illustration3   
,,fig4 #e4  ,illustration3 ,,fig4 #f4   
,the writer will take up next the       
question of pressures against the faces 
of sheeted trenches or retaining walls1 
in material of the same character as    
noted above4 ,referring to ,fig4 #b1 it 
is not reasonable to suppose that having
 passed the line1 ,r ,f ,j1 the         
character of the stresses due to the    
thrust of the material will change1 if  
bracing should be substituted for the   
material in the area1 ,w ,v ,j ,r1 or   
if1 as in ,fig4 #c1 canvas is rolled    
down along the lines1 ,e ,g and ,a ,o1  
and if1 as this section is excavated    
between the canvas faces1 temporary     
struts are erected1 there is no reason  
to believe that with properly adjusted  
weights at ,w or ,w#b1 an exact         
equilibrium of forces and conditions    

cannot be obtained4 ,or1 again1 if1 as  
in ,fig4 #e1 the face1 ,p ,q1 is sheeted
 and rodded back to the surface1 keying 
the rods taut1 there is undoubtedly a   
stable condition and one which could not
 fail in theory or practice1 nor can    
anyone1 looking at ,fig4 #e1 doubt that 
the top timbers are stressed more       
heavily than those at the bottom4 ,the  
assumption is that the tendency of the  
material to slide toward the toe causes 
it to wedge itself between the face of  
the sheeting on the one hand and some   
plane between the sheeting and the plane
 of repose on the other1 and that the   
resistance to this tendency will cause  
an arching thrust to be developed along 
or parallel to the lines1 ,a ,n1 ,b ,m1 
etc41 ,fig4 #b1 which are assumed to be 
the lines of repose1 or curves          
approximating thereto4 ,as the thrust is
 greatest in that material directly at  
the face1 ,a ,o1 ,fig4 #f1 and is       
nothing at the plane of repose1 ,c ,o1  
it may be assumed arbitrarily that the  

line1 ,b ,o1 bisecting this angle       
divides this area into two1 in one of   
which the weight resolves itself wholly 
into thrust1 the other being an area of 
no thrust1 or wholly of weight bearing  
on the plane of repose4 ,calling this   
line1 ,b ,o1 the haunch line1 the thrust
 in the area1 ,a ,o ,b1 is measured by  
its weight divided by the tangent of the
 angle1 ,p ,q ,r  phi1 which is the     
angle of repose2 that is1 the thrust at 
any given point1 ,r  ,r ,q  tan4 phi4   
,the writer suggests that1 in those     
materials which have steeper angles of  
repose than #de1 the area of pressure   
may be calculated as above1 the thrust  
being computed1 however1 as for an angle
 of #de degrees4  ,in calculating the   
bending moment against a wall or        
bracing1 there is the weight of the mass
 multiplied by the distance of its      
center of gravity vertically above the  
toe1 or1 approximately3                 
#b ,area1 ,a ,o ,b  weight per unit  ---
 height1                                

#c  where h  height1  ,w  weight per    
cubic foot of material  #ij lb41        
#ij - phi and beta  -------------       
#b  ,p  pressure per linear foot        
7vertically71                    h      
#b then ,p  h  ----- 7tan4 beta7  ,w    
--- h                     #b            
#c      #a     --- h#c ,w tan4 beta4    
#c  ,when the angle of repose1 phi1 is  
less than #de1 this result must be      
reduced by dividing by tan4 phi2 that   
is1         #a h  --- h#c tan4 beta     
tan4 phi4        #c  ,figs4 #a and #b1  
,plate ,,xxv1 show recently excavated   
banks of gravel and sand1 which1        
standing at a general angle of #de1 were
 in process of working1 that is1 there  
was continual slipping down of particles
 of the sand1 and it may be well to note
 that in time1 under exposure to weather
 conditions1 these banks would finally  
assume a slope of about #cc degrees4    
,they are typical1 however1 as showing  
the normal slope of freshly excavated   
sandy material1 and a slope which may be

 used in ordinary calculations4 ,the    
steps seen in ,plate ,,xxv show the     
different characteristics of ground in  
close proximity4 ,in ,fig4 #b1 ,plate   
,,xxvi1,d may be seen a typical bank of 
gravel and sand2 it shows the           
well-defined slope of sand adjacent to  
and in connection with the cohesive     
properties of gravel4  ,the next points 
to be considered are the more difficult 
problems concerning subaqueous or       
saturated earths4 ,the writer has made  
some experiments which appear to be     
conclusive1 showing that1 except in pure
 quicksand or wholly aqueous material1  
as described later1 the earth and water 
pressures act independently of each     
other4  ,for a better understanding of  
the scope and purpose of this paper1 the
 writer divides supersaturated or       
subaqueous materials into three classes3
  ,class ,a4--,firm materials1 such as  
coarse and fine gravels1 gravel and     
sands mixed1 coarse sands1 and fine     
sands in which there is not a large     

proportion of fine material1 such as    
loam1 clay1 or pure quicksand4  ,class  
,b4--,semi-aqueous materials1 such as   
fine sands in which there is a large    
proportion of clay1 etc41 pure clays1   
silts1 peats1 etc4  ,class ,c4--,aqueous
 materials1 such as pure quicksands1 in 
which the solid matter is so finely     
divided that it is amorphous and        
virtually held in suspension1 oils1     
quicksilver1 etc4  ,here it may be      
stated that the term1 quicksand1 is so  
illusive that a true definition of it is
 badly needed4 ,many engineers call     
quicksand any sand which flows under the
 influence of water in motion4 ,the     
writer believes the term should be      
applied only to material so soupy that  
its properties are practically the same 
as water under static conditions1 it    
being understood that any material may  
be unstable under the influence of water
 at sufficiently high velocities1 and   
that it is with a static condition1 or  
one approximately so1 that this paper   

deals4  ,a clear understanding of the   
firm materials noted in ,class ,a will  
lead to a better solution of problems   
dealing with those under ,class ,b1 as  
it is to this ,class ,a that the        
experiments largely relate4  ,the       
experiments noted below were made with  
varying material1 though the principal  
type used was a fine sand1 under the    
conditions in which it is ordinarily    
found in excavations1 with less than #dj
 voids and less than #aj of very fine   
material4  ,illustration3 ,,fig4 #g4    
,experiment ,no4 #b4--,the first of     
these experiments1 which in this series 
will be called ,no4 #b1 was simple1 and 
was made in order to show that this     
material does not flow readily under    
ordinary conditions1 when not coupled   
with the discharge of water under high  
velocity4 ,a bucket #ab in4 in diameter1
 containing another bucket #i in4 in    
diameter1 was used4 ,a #f by #f-;in4    
hole was cut in the bottom of the inner 
bucket4 ,about #c in4 of sand was first 

placed in the bottom of the larger      
bucket and it was partly filled with    
water4 ,the inside bucket was then given
 a false bottom and partly filled with  
wet sand1 resting on the sand in the    
larger bucket4 ,both were filled with   
water1 and the weight1 ,w1 ,fig4 #g1 on 
the arm was shifted until it balanced   
the weight of the inside bucket in the  
water1 the distance of the weight1 ,w1  
from the pivot being noted4 ,the false  
bottom was then removed and the inside  
bucket1 resting on the sand in the      
larger one1 was partly filled with sand 
and both were filled with water1 the    
conditions at the point of weighing     
being exactly the same1 except that the 
false bottom was removed1 leaving the   
sand in contact through the #f by       
#f-;in4 opening4 ,it is readily seen    
that1 if the sand had possessed the     
aqueous properties sometimes attributed 
to sand under water1 that in the inside 
bucket would have flowed out through the
 square hole in the bottom1 allowing it 

to be lifted by any weight in excess of 
the actual weight of the bucket1 less   
its buoyancy1 as would be the case if it
 contained only water instead of sand   
and water4 ,it was found1 however1 that 
the weight1 resting at a distance of    
more than nine-tenths of the original   
distance from the pivot1 would not raise
 the inside bucket4 ,on lifting this    
inside bucket bodily1 however1 the water
 at once forced the sand out through the
 bottom1 leaving a hole almost exactly  
the shape and size of the bottom        
orifice1 as shown in ,fig4 #a1 ,plate   
,,xxvii4 ,it should be stated that1 in  
each case1 the sand was put in in small 
handfuls and thoroughly mixed with      
water1 but not packed1 and allowed to   
stand for some time before the          
experiments were tried1 to insure the   
compactness of ordinary conditions4 ,it 
is seen from ,fig4 #a1 ,plate ,,xxvii1  
that the sand was stable enough to allow
 the bucket to be put on its side for   
the moment of being photographed1       

although it had been pulled out of the  
water a little less than #c min4        
,illustration3 ,,plate ,,xxvi1 ,,fig4   
#a4--,,types ,,of ,,arch ,,timbers      
,,used ,,in ,,bay ,,ridge ,,tunnel      
,,sewer4  ,illustration3 ,,plate ,,xxvi1
 ,,fig4 #b4--,,normal ,,slope ,,of      
,,loose ,,sand1 ,,gravel1 ,,and         
,,cemented ,,gravel1 ,,in ,,close       
,,proximity4  ,experiment ,no4 #c4--;,in
 order to show that the arching         
properties of sand are not destroyed    
under subaqueous conditions1 a small    
sand-box1 having a capacity of about #a 
cu4 ft41 and similar to that described  
in ,experiment ,no4 #a1 was made4 ,the  
bottom was cut out1 with the exception  
of a -in4 projection on two sides1 and a
 false bottom was placed below and      
outside of the original bottom1 with    
bolts running through it1 keying to     
washers on top of the sand1 with which  
the box was partly filled4 ,one side of 
the box contained a glass front1 in     
order that conditions of saturation     

could be observed4 ,the box of sand was 
then filled with water and1 after       
saturation had been completed and the   
nuts and washers had been tightened     
down1 the box was lifted off the floor4 
,there was found to be no tendency      
whatever for the bottom to fall away1   
showing conclusively that the arching   
properties had not been destroyed by the
 saturation of the sand4  ,the next     
three experiments were intended to show 
the relative pressure over any given    
area in contact with the water in the   
one case or sand and water in the other4
  ,illustration3 ,,fig4 #h4  ,experiment
 ,no4 #d4--,the apparatus for this      
experiment consisted of a #c-;in4 pipe  
about #d-;in4 long and connected with a 
-in4 goose-neck pipe #ag in4 high above 
the top of the bowl shown in ,fig4 #h   
and in ,fig4 #b1 ,plate ,,xxvii4 ,a     
loose rubber valve was intended to be   
seated on the upper face of the machined
 edge of the bowl and weighted down     
sufficiently to balance it against a    

head of water corresponding to the      
#ag-;in4 head in the goose-neck4 ,the   
bowl was then to be filled with sand and
 the difference1 if any1 noted between  
the weight required to hold the         
flap-valve down under the same head of  
water flowing through the sand4 ,the    
results of this experiment were not     
conclusive1 owing to the difficulty of  
making contact over the whole area of   
the sand and the rim of the bowl at the 
same time4 ,at times1 for instance1 less
 than #a lb4 would hold back the water  
indefinitely1 while1 again1 #b or #c lb4
 would be required as opposed to the #d 
lb4 approximate pressure required to    
hold down the clear water4 ,again1 at   
times the water would not flow through  
the neck at all1 even after several     
hours1 and after increasing the head by 
attaching a longer rubber tube thereto4 
,in view of these conditions1 this      
experiment would not be noted here1     
except that it unexpectedly developed   
one interesting fact4 ,in order to      

insure against a stoppage of water1 as  
above referred to1 gravel was first put 
into the bottom of the bowl and the     
flap-valve was then rubbed down and held
 tightly while the pipe was filled4 ,on 
being released1 the pressure of water   
invariably forced out the whole body of 
sand1 as shown in ,fig4 #b1 ,plate      
,,xxvii4 ,care was taken to see that the
 sand was saturated in each case1 and   
the experiment was repeated numberless  
times1 and invariably with the same     
result4 ,the sand contained about #dj of
 voids4 ,the deduction from this        
experiment is that the pressure of water
 is against rather than through sand and
 that any excess of voids occurring     
adjacent to a face against which there  
is pressure of water will be filled with
 sand1 excepting in so far1 of course1  
as the normal existing voids allow the  
pressure of the water to be transmitted 
through them4  ,illustration3 ,,plate   
,,xxvii1 ,,fig4 #a4--;,,experiment      
,,showing ,,properties ,,of ,,sand4     

,illustration3 ,,plate ,,xxvii1 ,,fig4  
#b4--,,sand ,,pushed ,,up ,,from ,,bowl 
,,by ,,water ,,pressure ,,through       
,,goose-,,neck4  ,if1 then1 the covering
 of sand over a structure is            
sufficiently heavy to allow arching     
action to be set up1 the structure      
against which the pressure is applied   
must be relieved of much of the pressure
 of water against the area of sand not  
constituted as voids acting outside of  
the arching area4 ,this is confirmed by 
the two following experiments3          
,experiment ,no4 #e4--,the same         
apparatus was used here as in           
,experiment ,no4 #b1 ,fig4 #g1 except   
that the inside bucket had a solid      
bottom4 ,the inside and outside buckets 
were filled with water and the point was
 noted at which the weight would balance
 the inside bucket at a point some #c   
in4 off the bottom of the outside       
bucket4 ,this point was measured1 and   
the bottom of the larger bucket was     
covered over with sand so that in       

setting solidly in the sand the inside  
bucket would occupy the same relative   
position as it did in the water4 ,the   
same weight was then applied and would  
not begin to lift the inner bucket4 ,for
 instance1 in the first part of the     
experiment the weight stood at #ab in4  
from the pivot1 while in the next step  
the weight1 standing at the end of the  
bar1 had no effect1 and considerable    
external pressure had to be exerted     
before the bucket could be lifted4      
,immediately after it was relieved1     
however1 the weight at #ab in4 would    
hold it clear of the sand4 ,no attempt  
was made to work the bucket into the    
sand2 the sand was leveled up and the   
bucket was seated on it1 turned once or 
twice to insure contact1 and then       
allowed to stand for some time before   
making the experiment4 ,no attempt was  
made to establish the relationship      
between sands of varying voids1 the     
general fact only being established1 by 
a sufficient number of experiments1 that

 the weight required to lift the bucket 
was more than double in sand having #dj 
of voids than that required to lift the 
bucket in water only4  ,illustration3   
,,fig4 #i4  ,experiment ,no4 #f4--,the  
apparatus for this experiment consisted 
essentially of a hydraulic chamber about
 #h in4 in diameter and #a ft4 high1 the
 top being removable and containing a   
collar with suitable packing1 through   
which a #b-;in4 piston moved freely up  
and down1 the whole being similar to the
 cylinder and piston of a large         
hydraulic jack1 as shown in ,fig4 #a1   
,plate ,,xxviii4 ,just below the collar 
and above the chamber there was a -in4  
inlet leading to a copper pipe and      
thence to a high-pressure pump4         
,attached to this there was a gauge to  
show the pressure obtained in the       
chamber1 all as shown in ,fig4 #i4 ,the 
purpose of the apparatus was to test the
 difference in pressure on any object   
submerged in clear water and on the same
 object buried in the sand under water4 

,it is readily seen that1 if pressure be
 applied to the water in this chamber1  
the amount of pressure 7as measured by  
the gauge7 necessary to lift the piston 
will be that due to the weight of the   
piston1 less its displacement1 plus the 
friction of the piston in the collar4   
,illustration3 ,,plate ,,xxviii1 ,,fig4 
#a4--;,,apparatus ,,for ,,measuring     
,,loss ,,of ,,pressure ,,in ,,subaqueous
 ,,materials4  ,illustration3 ,,plate   
,,xxviii1 ,,fig4 #b4--,,raising ,,roof  
,,of ,,battery ,,tubes1 ,,in ,,brooklyn1
 ,,by ,,bleeding ,,sand ,,through       
,,displaced ,,plates4  ,now1 if for any 
reason the bottom area of the piston    
against which the water pressure acts be
 reduced1 it will necessarily require a 
proportionate amount of increase in the 
pressure to lift this piston4 ,if1      
therefore1 it is found that #aj lb41 for
 illustration1 be required to lift the  
piston when plunged in clear water1 and 
#bj lb4 be required to lift it when     
buried in sand1 it can be assumed at    

once that the area of the piston has    
been reduced #ej by being buried in the 
sand1 eliminating the question of the   
friction of the sand itself around the  
piston4 ,in order to determine what this
 friction might be1 the writer arranged 
a table standing on legs above the      
bottom of the chamber1 allowing the     
piston to move freely through a hole in 
its center4 ,through this table pipes   
were entered 7as shown in part of ,fig4 
#i74 ,the whole was then placed in the  
chamber with the piston in place1 and   
the area above was filled with sand and 
water4 ,it is thus seen that1 the end of
 the piston being free and in clear     
water1 the difference1 if any1 between  
the pressure required to lift the piston
 when in clear water alone and in the   
case thus noted1 where it was surrounded
 by sand1 would measure the friction of 
the sand on the piston4 ,after several  
trials of this1 however1 it was clearly 
seen that the friction was too slight to
 be noted accurately by a gauge         

registering single pounds1 that is1 with
 a piston in contact with #f in4 of sand
 vertically1 a friction of #be lb4 per  
sq4 ft4 would only require an increase  
of #a4h lb4 on the gauge4 ,it is        
therefore assumed that the friction on  
so small a piston in sand need not be   
considered as a material factor in the  
experiments made4  ,the piston was      
plunged into clear water1 and it was    
found that the pressure required to lift
 it was about #d lb4 ,the cap was then  
taken off1 a depth of about #b in4 of   
sand was placed in the bottom of the    
chamber1 and then the piston was set in 
place and surrounded by sand to a depth 
of some #f in41 water being added so    
that the sand was completely saturated4 
,this was allowed to stand until it had 
regained the stability of ordinary sand 
in place1 whereupon the cap with the    
collar bearing was set in place over the
 piston1 the machine was coupled up1 and
 the pump was started4 ,a series of four
 experiments1 extending over a period of

 two or three days1 gave the following  
results3  ,test #a4--,the piston began  
to move at a pressure of #be lb4 ,the   
pressure gradually dropped to #g lb41 at
 which point1 apparently1 it came out of
 the sand1 and continued at #g lb4      
during the remainder of the test4  ,test
 #b4--,the piston was plunged back into 
the sand1 without removing the cap1 and 
allowed to stand for about #b hours4 ,no
 attempt was made to pack the sand or to
 see its condition around the piston1 it
 being presumed1 however1 that it had   
reasonable time to get a fair amount of 
set4 ,at slightly above #bj lb4 the     
piston began to move1 and as soon as a  
pocket of water accumulated behind the  
piston the pressure immediately dropped 
to #i lb4 and continued at this point   
until it came out of the sand4  ,test   
#c4--,the piston was plunged into the   
sand and hammered down without waiting  
for the sand to come to a definite set4 
,in this case the initial pressure shown
 by the gauge was #ag lb41 which        

immediately dropped to #h lb4 as soon as
 the piston had moved sufficiently far  
to allow water to accumulate below it4  
,test #d4--,the cap was again removed1  
the piston set up in place1 the sand    
compacted around it in approximately the
 same condition it would have had if the
 sand had been in place underground2 the
 cap was then set in place and1 after an
 hour1 the pump was started4 ,the       
pressure registered was #be lb4 and     
extended over a period of several       
seconds before there was any movement in
 the piston4 ,the piston responded      
finally without any increase of         
pressure1 and1 after lifting an inch or 
two1 the pressure gradually dropped to  
#aj lb41 where it remained until the    
piston came out of the sand4  ,the sum  
and average of these tests shows a      
relation of #bb lb4 for the piston in   
sand to about #h lb4 as soon as the     
volume of water had accumulated below   
it1 which would correspond very closely 
to a sand containing #dj of voids1 which

 was the characteristic of the sand used
 in this experiment4  ,the conclusions  
from this experiment appear to be       
absolutely final in illustrating the    
pressure due to water on a tunnel buried
 in sand1 either on the arch above or on
 the sides or bottom1 as well as the    
buoyant effect upon the tunnel bottom   
under the same conditions4  ,while the  
apparatus would have to be designed and 
built on a much larger scale in order to
 measure accurately the pressures due to
 sands and earths of varying            
characteristics1 it appears to be       
conclusive in showing the principle1 and
 near enough to the theoretical value to
 be taken for practical purposes in     
designing structures against water      
pressures when buried in sand or earth4 
,it should be carefully noted that the  
friction of the water through sand1     
which is always a large factor in       
subaqueous construction1 is virtually   
eliminated here1 as the water pressure  
has to be transmitted only some #f or #h

 in4 to actuate the base of the piston1 
whereas in a tunnel only half submerged 
this distance might be as many feet1 and
 would be a considerable factor4  ,it   
should be noted also that although the  
area subject to pressure is diminished1 
the pressure on the area remaining      
corresponds to the full hydrostatic     
head1 as would be shown by the pressure 
on an air gauge required to hold back   
the water1 except1 of course1 as it may 
be diminished more or less by friction4 
,the writer understands that experiments
 of a similar nature and with similar   
apparatus have been tried on clays and  
peats with results considerably higher2 
that is1 in one case1 there was a       
pressure of #dj lb4 before the piston   
started to move4  ,the following is     
given1 in part1 as an analysis and      
explanation of the above experiments and
 notes3  ,it is well known that if lead 
be placed in a hydraulic press and      
subjected to a sufficient pressure it   
will exhibit properties somewhat similar

 to soft clay or quicksand under        
pressure4 ,it will flow out of an       
orifice or more than one orifice at the 
same pressure4 ,this is due to the fact 
that practically voids do not exist and 
that the pressure is so great1 compared 
with the molecular cohesion1 that the   
latter is virtually nullified4 ,it is   
also theoretically true that solid stone
 under infinitely high pressure may be  
liquefied4 ,if in the cylinder of a     
hydraulic press there be put a certain  
quantity of cobblestones1 leaving a     
clearance between the top of the stone  
and the piston1 and if this space1      
together with the voids1 be filled with 
water and subjected to a great pressure1
 the sides or the walls of the cylinder 
are acted on by two pressures1 one      
almost negligible1 where they are in    
contact with the stone1 restraining the 
tendency of the stone to roll or slide  
outward1 and the other due to the       
pressure of the water over the area     
against which there is no contact of    

stone4 ,that this area of contact should
 be deducted from the pressure area can 
be clearly shown by assuming another    
cylinder with cross-sticks jammed into  
it1 as shown in ,fig4 #aj4 ,a glance at 
this figure will show that there is no  
aqueous pressure on the walls of the    
cylinder with which the ends of the     
sticks come in contact and the loss of  
the pressure against the walls due to   
this is equal to the least sectional    
area of the stick or tube either at the 
point of contact or intermediate        
thereto4  ,following this reasoning1 in 
,fig4 #aa it is found that an equivalent
 area may be deducted covering the least
 area of continuous contact of the      
cobblestones1 as shown along the dotted 
lines in the right half of the figure4  
,returning1 if1 when the pressure is    
applied1 an orifice be made in the      
cylinder1 the water will at once flow   
out under pressure1 allowing the piston 
to come in contact with the             
cobblestones4 ,if the flow of the water 

were controlled1 so as to stop it at the
 point where the stone and water are    
both under direct pressure1 it would be 
found that the pressures were totally   
independent of each other4 ,the aqueous 
pressure1 for instance1 would be equal  
at every point1 while the pressure on   
the stone would be through and along the
 lines of contact4 ,if this contact was 
reasonably well made and covered #dj of 
the area1 one would expect the stone1   
independently of the water1 to stand #dj
 of the pressure which a full area of   
solid stone would stand4 ,if this       
pressure should be enormously increased 
after excluding the water1 it would     
finally result in crushing the stone    
into a solid mass2 and if the pressure  
should be increased indefinitely1 some  
theoretical point would be reached1 as  
above noted1 where the stone would      
eventually be liquefied and would assume
 liquid properties4  ,illustration3     
,,fig4 #aj4  ,illustration3 ,,fig4 #aa4 
,the same general reasoning applies to  

pure sand1 sand being in effect         
cobblestones in miniature4 ,in pressing 
the piston down on dry sand it will be  
displaced into every existing abnormal  
void1 but will be displaced into these  
voids rather than pressed into them1 in 
the true definition of the word1 and    
while it would flow out of an orifice in
 the sides or bottom1 allowing the      
piston to be forced down as in a        
sand-jack1 it would not flow out of an  
orifice in the top of the piston1 except
 under pressures so abnormally high as  
to make the mass theoretically aqueous4 
,if the positions of cylinder and piston
 be reversed1 the piston pointing       
vertically upward and the sand bled into
 an orifice in or through it1 the void  
caused by the outflow of this sand would
 be filled by sand displaced by the     
piston pressing upward rather than by   
sand from above4  ,it was the knowledge 
of this principle which enabled the     
contractors to jack up successfully the 
roof of a long section of the cast-iron 

lined tubes under ,joralemon ,street in 
,brooklyn1 in connection with the       
reconstruction of the ,battery tubes at 
that point1 the method of operation1 as 
partly shown in ,fig4 #b1 ,plate        
,,xxviii1 being to cut through a section
 of the roof1 #d by #aj ft4 in area1    
through which holes were drilled and    
through which again the sand was bled1  
heavy pressure being applied from below 
through the medium of hydraulic jacks4  
,by a careful manipulation of both these
 operations1 sections of the roof of the
 above dimensions were eventually raised
 the required height of #cj in4 and     
permanently braced there in a single    
shift4  ,if water in excess be put into 
a cylinder containing sand1 and pressure
 be applied thereto1 the water1 if      
allowed to flow out of an orifice1 will 
carry with it a certain quantity of     
sand1 according to the velocity1 and the
 observation of this might easily give  
rise to the erroneous impression that   
the sand1 as well as the water1 was     

flowing out under pressure1 and1 as     
heretofore stated1 has caused many      
engineers and contractors to apply the  
term quicksand to any sand flowing      
through an orifice with water4  ,sand in
 its natural bed always contains some   
fine material1 and where this is largely
 less than the percentage of voids1 it  
has no material effect on the pressure  
exerted by the sand with or without     
water1 as above noted4 ,if1 however1    
this fine material be largely in excess 
of the voids1 it allows greater initial 
compression to take place when dry1 and 
allows to be set up a certain amount of 
hydraulic action when saturated4 ,if the
 base of the material be sand and the   
fill be so-called quicksand in excess of
 the voids1 pressure will cause the     
quicksand to set up hydraulic action1   
and the action of the piston will appear
 to be similar to that of a piston      
acting on purely aqueous material4      
,just here the writer desires to protest
 against considering semi-aqueous       

masses1 such as soupy sands1 soft       
concrete1 etc41 as exerting hydrostatic 
pressure due to their weight in bulk1   
instead of to the specific gravity of   
the basic liquid4 ,for instance1        
resorting again to the illustration of  
cubes and spheres1 it may be assumed    
that a cubical receptacle has been      
partly filled with small cubes of       
polished marble1 piled vertically in    
columns4 ,when this receptacle is filled
 with liquid around the piles of cubes  
there will be no pressure on the sides  
except that due to the hydrostatic      
pressure of the water at #fb lb4 ,the   
bottom1 however1 will resist a combined 
pressure due to the water and the weight
 of the cubes4 ,again1 assume that the  
receptacle is filled with small spheres1
 such as marbles1 and that water is then
 poured in4 ,the pressure due to the    
weight of the solids on the bottom is   
relieved by the loss in weight of the   
marbles due to the water1 and also to   
the tendency of the marbles to arch over

 the bottom1 and while the pressure on  
the sides is increased by this amount of
 thrust1 the aqueous pressure is still  
that of a liquid at #fb lb41 and it is  
inconceivable that some engineers1 in   
calculating the thrust of aqueous       
masses1 speak of it as a liquid         
weighing1 say1 #abj or #aej lb4 per cu4 
ft42 as well might they expect to anchor
 spherical copper floats in front of a  
bulkhead and expect the hydrostatic     
pressure against this bulkhead to be    
diminished because the actual volume and
 weight of the water directly in front  
of the bulkhead has been diminished4    
,those who have had experience in tying 
narrow deep forms for concrete with     
small wires or bolts and quickly filling
 them with liquid concrete1 must realize
 that no such pressures are ever        
developed as would correspond to liquids
 of #aej lb4 per cu4 ft4 ,if the solid  
material in any liquid is agitated1 so  
that it is virtually in suspension1 it  
cannot add to the pressure1 and if      

allowed to subside it acts as a solid1  
independently of the water contained    
with it1 although the water may change  
somewhat the properties of the material1
 by increasing or changing its cohesion1
 angle of repose1 etc4 ,that is1 in     
substance1 those particles which rest   
solidly on the bottom and are in contact
 to the top of the solid material1 do   
not derive any buoyancy from the water1 
while those particles not in contact    
with the bottom directly or through     
other particles1 lose just so much      
weight through buoyancy4 ,if1 then1 the 
vertical depth of the earthy particles  
or sand above the bottom is so small    
that the arching effect against the     
sides is negligible1 the full weight of 
the particles in contact1 directly or   
vicariously1 with the bottom acts as    
pressure on the bottom1 while the full  
pressure of the water acts through the  
voids or on them1 or is transmitted     
through material in contact with the    
bottom4  ,referring now to materials    

such as clays1 peats1 and other soft or 
plastic materials1 it is idle to assume 
that these do not possess               
pressure-resisting and arching          
properties4 ,for instance1 a soft clay  
arch of larger dimensions1 under the    
condition described early in this paper1
 would undoubtedly stand if the rods    
supporting the intrados of the arch were
 keyed back to washers covering a       
sufficiently large area4  ,the fact that
 compressed air can be used at all in   
tunnel work is evidence that            
semi-aqueous materials have arching     
properties1 and the fact that blows     
usually occur in light cover is further 
evidence of it4  ,when air pressure is  
used to hold back the water in faces of 
large area1 bracing has to be resorted  
to4 ,this again shows that while full   
hydrostatic pressure is required to hold
 back the water1 the pressure of the    
earth is in a measure independent of it4
  ,in a peaty or boggy material there is
 a condition somewhat different1 but    

sufficiently allied to the soft clayey  
or soupy sands to place it under the    
same head in ordinary practice4 ,it is  
undoubtedly true that piles can be      
driven to an indefinite depth in this   
material1 and it is also true that the  
action of the pile is to displace rather
 than compress1 as shown by the fact of 
driving portions of the tunnels under   
the ,north ,river for long distances    
without opening the doors of the shield 
or removing any of the material4 ,the   
case of filling in bogs or marshes1     
causing them to sink at the point of    
filling and rise elsewhere1 is readily  
explained by the fact that the water is 
confined in the interstices of the      
material1 admitting of displacement but 
no compression4  ,the application of the
 above to pressures over tunnels in     
materials of ,class ,a is that the sand 
or solid matter is virtually assumed to 
be a series of columns with their bases 
in such intimate contact with the tunnel
 roof that water cannot exert pressure  

on the tunnel or buoyancy on the sand at
 the point of contact1 and that if these
 columns are sufficiently deep to have  
their upper portions wholly or partly   
carried by the arching or wedging       
action1 the pressure of any water on    
their surfaces is not transferred to the
 tunnel1 and the only aqueous pressure  
is that which acts on the tunnel between
 the assumed columns or through the     
voids4  ,let l  exterior width of       
tunnel1     d  depth of cover1 as3      
,d,w  depth1 water to roof1       ,d,e  
earth to roof1       ,d,x        of     
cover of earth necessary to arching     
stability1  that is3             l      
_/ #ij - phi  ,d,x  ----- 7 tan4        
-------------   phi 7              #b   
#b       _/       l                phi  
----- tan4  7#de  ------- 71       #b   
#b     where phi  angle of repose1      
and ,d,w  ,d,e  ,d,x4  ,then the        
pressure on any square foot of roof1 as 
,v,p as at the base of any vertical     
ordinate1 as #i in ,fig4 #b1  ,v,o1     

,w,e  weight per cubic foot of earth    
7#ij lb471    ,w,w                      
water 7#fb lb471 we have  ,v,p  ,v,o    
,w,e  ,d,w  ,w,w  #j4dj                 
#a     ,v,o  #ij  ,d,w  #fb---  #j4d    
,v,o #ij  ,d,w  #be4                    
#b  ,and for horizontal pressure3  ,ph  
the horizontal pressure at any abscissa 
7#aj71 ,fig4 #b1  ,a#aj at depth of     
water ,d,w#a is               ,a#aj  #ij
                  #a   ,ph              
---------------  ,d,w#a  #fb---  #j4d   
tan4 phi                   #b           
,a#aj  #ij     ---------------  ,d,w#a  
#be4        tan4 phi  ,the only question
 of serious doubt is at just what depth 
the sand is incapable of arching itself1
 but1 for purposes of safety1 the writer
 has put this at the point1 ,f1 as noted
 above1  ,d,x1 although he believes that
 experiments on a large scale would show
 it to be nearer #j4fg;,d,x1 above which
 the placing of additional back-fill    
will lighten the load on the structure4 
,we have1 then1 for ,d,e  ,d,x1 the     

weight of the total prism of the earth  
plus the water in the voids1 plus the   
added pressure of the water above the   
earth prism1 that is3  ,the pressure per
 square foot at the base of any vertical
 ordinate  ,v,p                         
#a ,v,p  ,d,e  #ij  ,d,e  #fb---  #j4dj 
#b                                 #a   
7 ,d,w - ,d,e 7  #fb---4                
#b  ,to those who may contend that water
 acting through so shallow a prism of   
earth would exert full pressure over the
 full area of the tunnel1 it may be     
stated that the water cannot maintain   
pressure over the whole area without    
likewise giving buoyancy to the sand    
previously assumed to be in columns1 in 
which case there is the total weight of 
the water plus the weight of the prism  
of earth1 less its buoyancy in water1   
that is                         #a      
#a ,v,p  ,d,w  #fb---  ,d,e  7 #ij -    
#fb--- 71                        #b     
#b  which1 by comparison with the former
 method1 would appear to be less safe in

 its reasoning4  ,illustration3         
,,combined ,,earth ,,and ,,water        
,,pressures4 ,,fig4 #ab4  ,next is the  
question of pressure against a wall or  
braced trench for materials under ,class
 ,a4 ,the pressure of sand is first     
calculated independently1 as shown in   
,fig4 #f4 ,reducing this to a basis of  
#ajj lb4 for each division of the scale 
measured horizontally1 as shown1 gives  
the line1 ,b ,o1 ,fig4 #ab1 measuring   
the outside limit of pressure due to the
 earth1 the horizontal distance at any  
point between this line and the vertical
 face equalling the pressure against    
that face divided by the tangent of the 
angle of repose1 which in this case is  
assumed to be #de1 equalling unity4 ,if 
the water pressure line1 ,c ,f1 is      
drawn1 it shows the relative pressure of
 the water4 ,in order to reduce this to 
the scale of #ajj lb4 horizontal        
measurement1 the line1 ,c ,e1 is drawn1 
representing the water pressure to      
scale1 that is1 so that each horizontal 

measurement of the scale gives the      
pressure on the face at that point2 and1
 allowing #ej for voids1 halving this   
area gives the line1 ,c ,d1 between     
which and the vertical face any         
horizontal line measures the water      
pressure4 ,extending these pressure     
areas where they overlap gives the line1
 ,b ,d1 which represents the total      
pressure against the face1 measured     
horizontally4  ,next1 as to the question
 of buoyancy in ,class ,a materials4 ,if
 a submerged structure rests firmly on a
 bottom of more or less firm sand1 its  
buoyancy1 as indicated by the           
experiments1 will only be a percentage  
of its buoyancy in pure water1          
corresponding to the voids in the sand4 
,in practice1 however1 an attempt to    
show this condition will fail1 owing to 
the fact that in such a structure the   
water will almost immediately work under
 the edge and bottom1 and cause the     
structure to rise1 and the test can only
 be made by measuring the difference in 

uplift in a heavier-than-water          
structure1 as shown in ,experiment ,no4 
#e4 ,for1 if a structure lighter than   
the displaced water be buried in sand   
sufficiently deep to insure it against  
the influx of large volumes of water    
below1 it will not rise4 ,that this is  
not due entirely to the friction of the 
solid material on the sides has been    
demonstrated by the observation of      
subaqueous structures1 which always tend
 to subside rather than to lift during  
or following disturbance of the         
surrounding earth4  ,the following is   
quoted from the paper by ,charles ,m4   
,jacobs1 ,m4 ,am4 ,soc4 ,c4 ,e41 on the 
,north ,river ,division of the          
,pennsylvania ,railroad ,tunnels3,e     
,there was considerable subsidence in   
the tunnels during      construction and
 lining1 amounting to an average of     
#j4cd ft4      between the bulkhead     
lines4 ,this settlement has been        
constantly      decreasing since        
construction1 and appears to have been  

due almost      entirely to the         
disturbances of the surrounding         
materials during      construction4 ,the
 silt weighs about #ajj lb4 per cu4 ft4 
99 99 99 and      contains about #ch of 
water4 ,it was found that whenever this 
material was disturbed outside the      
tunnels a displacement of the           
tunnels followed4  ,this in substance   
confirms observations made in the       
,battery tubes that subsidence of the   
structure followed disturbance of the   
outside material1 although theoretically
 the tubes were buoyant in the aqueous  
material4  ,the writer would urge1      
however1 that1 in all cases of submerged
 structures only partially buried in    
solid material1 excess weighting be used
 to cover the contingencies of          
vibration1 oscillation1 etc41 to which  
such structures may be subjected and    
which may ultimately allow leads of     
water to work their way underneath4  ,on
 the other hand1 he urges that1 in cases
 of floor areas of deeply submerged     

structures1 such as tunnels or cellars1 
the pressure to be resisted should be   
assumed to be only slightly in excess of
 that corresponding to the pressure due 
to the water through the voids4  ,the   
question of pressure1 etc41 in ,class   
,b1 or semi-aqueous materials will be   
considered next4 ,of these materials1 as
 already shown1 there are two types3 7a7
 sand in which the so-called quicksand  
is largely in excess of any normal      
voids1 and 7b7 plastic and viscous      
materials4 ,the writer believes that    
these materials should be treated as    
mixtures of solid and watery particles1 
in the first of which the quicksand1 or 
aqueous portion1 being virtually in     
suspension1 may be treated as water1 and
 it must be concluded that the action   
here will be similar to that of sand and
 pure water1 giving a larger value to   
the properties of water than actually   
exists4 ,if1 for instance1 it should be 
found that such a mixture contained #dj 
of pure water1 the writer would estimate

 its pressure on or against a structure 
as 7a7 that of a moist sand standing at 
a steep angle of repose1 and 7b7 that of
 clear water1 an allowance of #fj of the
 total volume being assumed1 and the sum
 of these two results giving the total  
pressure4 ,until more definite data can 
be obtained by experiments on a larger  
scale1 this assumed value of #fj of the 
total volume for the aqueous portion may
 be taken for all conditions of         
semi-aqueous materials1 except1 of      
course1 where the solid and aqueous     
particles may be clearly defined1 the   
pressures being computed as described in
 the preceding pages4  ,as to the       
question of pure quicksand 7if such     
there be7 and other aqueous materials of
 ,class ,c1 such as water1 oil1 mercury1
 etc41 it has already been shown that   
they are to be considered as liquids of 
their normal specific gravity2 that is1 
in calculating the air pressure         
necessary to displace them1 one should  
consider their specific gravity only1 as

 a factor1 and not the total weight per 
volume including any impurities which   
they might contain undissolved4  ,in    
order to have a clearer conception of   
aqueous and semi-aqueous materials and  
their action1 they must be viewed under 
conditions not ordinarily apparent4 ,for
 instance1 ideas of so-called quicksand 
are largely drawn from seeing structures
 sinking into it1 or from observing it  
flowing through voids in the sheeting or
 casing4 ,the action of sand and water  
under pressure is viewed during or after
 a slump1 when the damage is being done1
 or has been done1 whereas the correct  
view-point is under static conditions1  
before the slump takes place4  ,the     
following is quoted from the report of  
,mr4 ,c4,m4 ,jacobs1 ,chief ,engineer of
 the ,east ,river ,gas ,tunnel1 built in
 #ahib-ic3       ,we found that the     
material which had heretofore been firm 
or stiff      had1 under erosion1       
obtained a soup-like consistency1 and   
that a      huge cavity some #c ft4 wide

 and #bf ft4 deep had been washed up    
toward the river bed4  ,this would      
probably be a fair description of much  
of the material of this class met with  
in such work1 if compressed air had not 
been used4 ,the writer believes that in 
soft material surrounding submerged     
structures the water actually contained 
in the voids is not infrequently1 after 
a prolonged period of rest1 cut off     
absolutely from its sources of pressure 
and that contact with these sources of  
pressure will not again be resumed until
 a leak takes place through the         
structure2 and1 even when there is a    
small flow or trickling of water through
 such material1 it confines itself to   
certain paths or channels1 and is       
largely excluded from the general mass4 
,the broad principle of the bearing     
power of soil has been made the subject 
of too many experiments and too much    
controversy to be considered in a paper 
which is intended to be a description of
 experiments and observed data and notes

 therefrom4 ,the writer is of the       
opinion1 however1 that entirely too     
little attention has been given to this 
bearing power of the soil2 that while   
progress has been made in our knowledge 
of all classes of materials for         
structures1 very little has been done   
which leads to any real knowledge of the
 material on which the foundation rests4
 ,for instance1 it is inconceivable that
 #a or #b tons may sometimes be allowed 
on a square foot of soft clay1 while the
 load on firm gravel is limited to from 
#d to #f tons4 ,the writer's practical  
observations have convinced him that it 
is frequently much safer to put four    
times #f tons on a square foot of gravel
 than it is to put one-fourth of #b tons
 on a square foot of soft clay4  ,in    
connection with the bearing power of    
soil1 the writer also believes that too 
little study has been given to the      
questions of the lateral pressure of    
earth1 and he desires to quote here from
 some experiments described in a book,f 

published in ,england in #ahgf1 to which
 his attention has recently been called4
 ,this book appears to have been        
intended for young people1 but it is of 
interest to note the following          
quotations from a chapter entitled      
,sand4 ,this chapter begins by stating  
that3       ,during the course of a     
lecture on the ,suez ,canal by ,mr4     
,john ,h4      ,pepper1 which was       
delivered nightly by him at the         
,polytechnic      ,institute in ,london1
 he illustrated his lecture by some     
experiments      designed to exhibit    
certain properties of sand1 which had   
reference      to the construction of   
the ,suez ,canal1 and it is stated that 
though      the properties in question  
were by no means to be classed among    
recent discoveries1 the experiments were
 novel in form and served      to       
interest the public audience4  ,further 
quotation follows3       ,when the ,suez
 ,canal was projected1 many prophesied  
evil to the      undertaking1 from the  

sand in the desert being drifted by the 
wind      into the canal1 and others    
were apprehensive that where the canal  
was cut through the sand the bottom     
would be pushed up by the      pressure 
on the banks 99 99 994       ,the       
principle of lateral pressure may now be
 strikingly      illustrated by taking  
an ,american wooden pail and1 having    
previously cut a large circular hole in 
the bottom1 this is now      covered    
with fine tissue paper1 which should be 
carefully pasted on      to prevent the 
particles of sand from flowing through  
the small      openings between the     
paper and the wood 99 99 99 and being   
placed      upright and rapidly filled  
with sand1 it may be carried about by   
the handle without the slightest fear of
 the weight of the sand      breaking   
through the thin medium4 99 99 99       
,probably one of the most convincing    
experiments is that which may      be   
performed with a cylindrical tube #ah   
in4 long and #b in4 in      diameter1   

open at both ends4 ,a piece of tissue   
paper is carefully      pasted on one   
end1 so that when dry no cracks or      
interstices are      left4 ,the tube is 
filled with dry sand to a height of say 
#ab in4 ,in      the upper part is      
inserted a solid plug of wood #ab in4   
long and of      the same or very nearly
 the same diameter as the inside of the 
tube1 so that it will move freely up and
 down like the piston of an      air    
pump4 ,the tube1 sand1 and piston being 
arranged as described1      may now be  
held by an assistant and the            
demonstrator1 taking a      sledge      
hammer1 may proceed to strike steadily  
on the end of the      piston and1      
although the paper will bulge out a     
little1 the force      of the blow will 
not break it4       ,if the assistant   
holding the tube allows it to jerk or   
rebound      after each blow of the     
hammer1 the paper may break1 because air
 and      sand are driven down by the   
succeeding blow1 and therefore it must  

be held steadily so that the piston     
bears fairly on the sand each      time4
       ,a still more conclusive and     
striking experiment may be shown with   
a framework of metal constructed to     
represent a pail1 the sides of          
which are closed up by pasting sheets of
 tissue paper inside and      over the  
lower part4 ,as before demonstrated1    
when a quantity of      sand is poured  
into the pail the tissue paper casing at
 the bottom      does not break1 but if 
a sufficient quantity is used the sides 
formed of tissue paper bulge out and    
usually give way in      consequence of 
the lateral pressure exerted by the     
particles of      sand4  ,the writer has
 made the second experiment noted1 with 
special apparatus1 and finds that with  
tissue paper over the bottom of a       
#b-;in4 pipe1 #ae in4 long1 about #ab   
in4 of sand will stand the blow of a    
heavy sledge hammer1 transmitted through
 a wooden piston1 at least once and     
sometimes two or three times1 while     

heavy blows given with a lighter hammer 
have no effect at all4 ,that this is not
 due in any large measure to inertia can
 be shown by the fact that more than    
#bjj lb4 can safely be put on top of the
 wooden piston4 ,it cannot be accounted 
for entirely by the friction1 as the    
removal of the paper allows the sand to 
drop in a mass4 ,the explanation is that
 the pressure is transmitted laterally  
to the sides1 and as the friction is    
directly proportional to the pressure1  
the load or effect of the blow is       
carried by the proportional increase in 
the friction1 and any diaphragm which   
will carry the direct bottom load will  
not have its stresses largely increased 
by any greater loading on top4  ,the    
writer believes that experiments will   
show that in a sand-jack the tendency   
will be for the sides to burst rather   
than the bottom1 and that the outflow   
from an orifice at or near the bottom is
 not either greatly retarded or         
accelerated by ordinary pressure on top4

 ,the occurrence of abnormal voids1     
however1 causes the sand to be displaced
 into them4  ,the important             
consideration of this paper is that all 
the experiments and observations noted  
point conclusively to the fact that     
pressure is transmitted laterally       
through ground1 most probably along or  
nearly parallel to the angles of repose1
 or in cases of rock or stiff material1 
along a line which1 until more          
conclusive experiments are made1 may be 
taken as a mean between the horizontal  
and vertical1 or approximately #de      
degrees4 ,there is no reason to believe 
that this is not the case throughout the
 entire mass of the earth1 that each    
cubic foot1 or yard1 or mile is         
supported or in turn supports its       
neighboring equivalent along such lines4
 ,the theory is not a new one1 and its  
field is too large to encompass within  
the limits of a single paper1 but1 for  
practical purposes1 and within the      
limited areas to which we must          

necessarily be confined1 the writer     
believes it can be established beyond   
controversy as true4 ,certain it is that
 no one has yet found1 in ground free   
from water pressure or abnormal         
conditions1 any evidence of greater     
pressure at the bottom of a deep shaft  
or tunnel than that near the surface4   
,pressures due to the widening of mines 
beyond the limits of safety must not be 
taken as a controversion of this        
statement1 as all arches have limits of 
safety1 more especially if the useless  
material below the theoretical intrados 
is only partly supported1 or is allowed 
to be suspended from the natural arch4  
,the writer believes1 also1 that the    
question of confined foundations1 in    
contradistinction to that of the        
spreading of foundations1 may be worthy 
of full discussion1 as it applies to    
safe and economical construction1 and he
 offers1 without special comment1 the   
following observations3  ,he has found  
that1 in soft ground1 results are often 

obtained with small open caissons sunk  
to a depth of a few feet and cleaned out
 and filled with concrete1 which offer  
much better resistance than spreading   
the foundation over four or five times  
the equivalent area4  ,he has found that
 small steel piles and coffer-dams1 from
 #a-;ft4 cylinders to coffer-dams #d or 
#e ft4 square1 sunk to a depth of only  
#a or #b ft4 below adjacent excavations 
in ordinary sand1 have safely resisted  
loads four or five times as great as    
those usually allowed4  ,he believes    
that short cylinders1 cleaned out and   
filled with concrete1 or coffer-dams of 
short steel piling with the surface     
cleaned out to a reasonable depth and   
filled with concrete horizontally       
reinforced1 will1 in many instances1    
give as good results as1 and1 in most   
cases1 very much better than1 placing   
the foundation on an equivalent number  
of small long piles or a proportionately
 greater spread of foundation area1 the 
idea being that the transmission of     

pressure to the sides of the coffer-dam 
will not only confine the side thrust1  
but will also transfer the loading in   
mass to a greater depth where the       
resistance to lateral pressure in the   
ground will be more stable2 that is1 the
 greater depth of foundation is gained  
without the increased excessive loading1
 or necessity for deep excavation4  ,as 
to the question of the bearing value and
 friction on piles1 the writer believes 
that while the literature on engineering
 is full of experimental data relating  
to friction on caissons1 there is little
 to show the real value of friction on  
piles4 ,the assumption generally made of
 an assumed bearing value1 and the      
deduction therefrom of a value for the  
skin friction is fallacious4            
,distinction1 also1 is not made1 but    
should be clearly drawn between skin    
friction1 pure and simple1 on smooth    
surfaces1 and the friction due to       
pressure4 ,too often the bearing value  
on irregular surfaces as well as the    

bearing due to taper in piles1 and      
lastly the resistance offered by        
binding1 enter into the determination of
 so-called skin friction formulas4 ,the 
essential condition of sinking a caisson
 is keeping it plumb2 and binding1 which
 is another way of writing increased    
bearing value1 will oftentimes be fatal 
to success4  ,the writer believes that a
 series of observations on caissons sunk
 plumb under homogeneous conditions of  
ground and superficial smoothness will  
show a proportional increase of skin    
friction per square foot average for    
each increase in the size of caissons1  
as well as for increase of depth in the 
sinking up to certain points1 where it  
may finally become constant1 as will be 
shown later4 ,the determination of the  
actual friction or coefficient of       
friction between the surfaces of the    
pile and the material it encounters1 is 
not difficult to determine4 ,in sand it 
is approximately #dj of the pressure for
 reasonably smooth iron or steel1 and   

#de of the pressure for ordinary wood   
surfaces4 ,if1 for instance1 a long     
shaft be withdrawn vertically from      
moulding sand1 the hole may remain      
indefinitely as long as water does not  
get into it or it does not dry out4     
,this is due to the tendency of the sand
 to arch itself horizontally over small 
areas4 ,the same operation cannot be    
performed on dry sand1 as the arching   
properties1 while protecting the pile   
from excessive pressure due to excessive
 length1 will not prevent the loose sand
 immediately surrounding the pile from  
exerting a constant pressure against the
 pile1 and it is of this pressure that  
#de may be taken as the real value of   
skin friction on piles in dry sand4  ,in
 soft clays or peats which are displaced
 by driving1 the tendency of this       
material to flow back into the original 
space causes pressure1 of which the     
friction will be a measured percentage4 
,in this case1 however1 the friction    
itself between the material and the     

clays or peat is usually very much less 
than #dj1 and it is for this reason that
 piles of almost indefinite length may  
be driven in materials of this character
 without offering sufficient resistance 
to be depended on1 as long as no good   
bearing ground is found at the point4   
,if this material is under water1 and is
 so soft as to be considered            
semi-aqueous1 the pressure per square   
foot will increase in diminishing       
proportion to the depth1 and the        
pressure per area will soon approach and
 become a constant1 due to the          
resistance offered by the lateral       
arching of the solid material2 whereas1 
in large circular caissons1 or caisson  
shafts1 where the horizontal arching    
effect is virtually destroyed1 or at    
least rendered non-effective until a    
great depth is reached1 the pressure    
must necessarily vary under these       
conditions proportionately to the depth 
and size of the caisson in semi-aqueous 
material4 ,on the other hand1 in large  

caisson shafts1 especially those which  
are square1 the pressure at the top due 
to the solid material will also increase
 proportionately to the depth1 as       
already explained in connection with the
 pressures of earth against sheeting and
 retaining walls4  ,the writer believes 
that the pressure on these surfaces may 
be determined with reasonable accuracy  
by the formulas already given in this   
paper1 and with these pressures1        
multiplied by the coefficient of        
friction determined by the simplest     
experiment on the ground1 results may be
 obtained which will closely approximate
 the actual friction on caissons at     
given depths4 ,the friction on caissons1
 which is usually given at from #bjj to 
#fjj lb4 per sq4 ft41 is frequently     
assumed to be the same on piles #ab in4 
or less in diameter1 whereas the        
pressures on these surfaces1 as shown1  
are in no way comparable4  ,the         
following notes and observations are    
given in connection with the skin       

friction and the bearing value of piles3
  ,the writer has in his possession a   
copy of an official print which was     
recently furnished to bidders in        
connection with the foundation for a    
large public building in ,new ,york     
,city4 ,the experiments were made on    
good sand at a depth of approximately   
#dc ft4 below water and #dg ft4 below an
 adjacent excavation4 ,in this instance 
a #af-;in4 pipe was sunk to the depth   
stated1 cleaned out1 and a #ad-;in4     
piston connected to a #aj-;in4 pipe was 
inserted and the ground at the bottom of
 the #af-;in4 pipe subjected to a       
loading approximating #bh tons per sq4  
ft4 ,after an initial settlement of     
nearly #c in41 there was no further     
settlement over an extended period1     
although the load of #bh tons per sq4   
ft4 was continued4  ,in connection with 
some recent underpinning work1 #ad-;in4 
hollow cylindrical piles #f ft4 long    
were sunk to a depth of #f ft4 with an  
ordinary hand-hammer1 being excavated as

 driven4 ,these piles were then filled  
with concrete and subjected to a loading
 in some cases approximating #fj tons4  
,after a settlement ranging from #i to  
#ac in41 no further settlement took     
place1 although the loading was         
maintained for a considerable period4   
,in connection with some other pile     
work1 the writer has seen a #aj-;in4    
pipe1 #c_/h in4 thick1 #d ft4 below the 
bottom of an open cylinder1 at a depth  
of about #bj ft41 sustain in gravel and 
sand a load approximating #ej tons when 
cleaned out to within #b ft4 of the     
bottom4  ,he has seen other cylindrical 
piles with a bearing ring of not more   
than  in4 resting on gravel at a depth  
of from #bj to #cj ft41 cleaned out     
practically to the bottom1 sustain a    
measured load of #fj tons without       
settlement4  ,as to skin friction in    
sand1 a case came under his observation 
wherein a #ad-;in4 hollow cylindrical   
pile which had stood for #bh days at a  
depth of about #cj ft4 in the sand1 was 

cleaned out to its bottom and subjected 
to hydraulic pressure1 measured by a    
gauge1 and sunk #b ft4 into the sand    
without any pressure being registered on
 the gauge4 ,it should be explained1    
however1 that the gauge could be        
subjected to a pressure of #bej lb41    
equal to a total pressure of #g1jjj lb4 
on the piston of the jack without       
registering1 which corresponded1        
assuming it all as skin friction1 to a  
maximum of not more than #gh lb4 per sq4
 ft41 but it should be noted that this  
included bearing value as well1 and that
 the pressure was very far from #g1jjj  
lb41 in all probability1 at the         
beginning of the test4  ,in the case of 
the ,california stove-pipe wells driven 
by the ,board of ,water ,supply on ,long
 ,island1 the writer is informed that   
one of these tubes1 #ab in4 in diameter1
 was sunk to a depth of #hej ft4 ,in    
doing this work the pile was excavated  
below the footing with a sand pump and  
was then sunk by hydraulic pressure4    

,assuming the maximum capacity of the   
jacks at #ajj tons1 which is not        
probable1 the skin friction could not   
have amounted to more than #ge lb4 per  
sq4 ft4 ,it cannot be assumed in this   
case that the excavation of the material
 below the pile relieved the skin itself
 of some of its friction1 as the        
operation consumed more than #f weeks1  
and1 even if excess material was        
removed1 it is certain that a large     
percentage of it would have had time to 
adjust itself before the operation was  
completed4  ,illustration3 ,,plate      
,,xxix1 ,,fig4 #a4--;,a #ad-;,,gauge1   
#ad-;,,in41 ,,hollow                    
7,,non-,,telescopic71 ,,california      
,,stove-,,pipe ,,pile ,,which ,,met     
,,impenetrable ,,material4              
,illustration3 ,,plate ,,xxix1 ,,fig4   
#b4--;,,chenoweth ,,pile1 ,,penetrating 
,,hard ,,material4  ,in connection with 
this1 the writer may call attention to  
the fact that piles driven in silt along
 the ,north ,river1 and in soft material

 at other places1 are sometimes #ij ft4 
in length1 and even then do not offer   
sufficient resistance to be depended on 
for loading4 ,this is due to the fact   
that the end of the pile does not bear  
in good material4  ,the relation between
 bearing value and skin friction on a   
pile1 where the end bearing is in good  
material1 is well shown by a case where 
a wooden pile,g struck solid material1  
was distorted under the continual blows 
of the hammer1 and was afterward        
exposed4 ,it is also shown in the case  
of a #ad-;in4 ,california stove-pipe    
pile1 ,no4 #ad gauge1 the point of which
 met firm material4 ,the result1 as     
shown by ,fig4 #a1 ,plate ,,xxix1 speaks
 for itself4 ,fig4 #b1 ,plate ,,xxix1   
shows a ,chenoweth pile which was an    
experimental one driven by its designer4
 ,this pile1 after getting into hard    
material1 was subjected to the blow of a
 #d1jjj-lb4 hammer falling the full     
length of the pile-driver1 and the only 
result was to shatter the head of the   

pile1 and not cause further penetration4
 ,mr4 ,chenoweth has stated to the      
writer that he has found material so    
compact that it could not be penetrated 
with a solid pile--either with or       
without jetting--which is in line with  
the writer's experience4  ,the writer   
believes that the foregoing notes will  
show conclusively that the factor to be 
sought in pile work is bearing value    
rather than depth or skin friction1 and1
 however valuable skin friction may be  
in the larger caissons1 it cannot be    
depended on in the case of small piles1 
except in values ranging from #be to    
#ajj lb4 per sq4 ft4  ,in conclusion1 he
 desires to thank the following         
gentlemen1 who have contributed to the  
success of the experiments noted herein3
 ,mr4 ,james ,w4 ,nelson1 of ,richard   
,dudgeon1 ,new ,york2 ,mr4 ,george      
,noble1 of ,john ,simmons and ,company1 
,new ,york2 and ,mr4 ,pendleton1 of     
,hindley and ,pendleton1 ,brooklyn1     
,n4,y42 all of whom have furnished      

apparatus for the experiments and have  
taken an interest in the results4 ,and  
lastly1 he desires especially to thank  
,mr4 ,f4,l4 ,cranford1 of the ,cranford 
,company1 for men and material with     
which to make the experiments and       
without whose co-operation it would have
 been impracticable for the writer to   
have made them4  ,throughout this paper 
the writer has endeavored1 as far as    
possible1 to deduce from his            
observations and from the observations  
of others1 as far as he has been able to
 obtain them1 practical data and        
formulas which may be of use in         
establishing the relationship between   
the pressure1 resistance1 and stability 
of earths2 and1 while he does not wish  
to dictate the character of the         
discussion1 he does ask that those who  
have made observations of a similar     
character or who have available data1   
will1 as far as possible1 contribute the
 same to this discussion4 ,it is only by
 such observations and experiments1 and 

deductions therefrom1 that engineers may
 obtain a better knowledge of the       
handling of such materials4  ,the writer
 believes that too much has been taken  
for granted in connection with earth    
pressures and resistance2 and that1 far 
too often1 observations of the results  
of natural laws have been set down as   
phenomena4 ,he believes that1 both in   
experimenting and observing1 the        
engineer will frequently find what is   
being looked for or expected and will   
fail to see the obvious alternative4 ,he
 may add that his own experiments and   
observations may be criticized for the  
same reason1 and he asks1 therefore1    
that all possible light be thrown on    
this subject4 ,a comparative study of   
much of our expert testimony or of the  
plans of almost any of the structures   
designed in connection with their       
bearing upon earth1 or resistance to    
earth pressure1 will show that under the
 present methods of interpretation of   
the underlying principles governing the 

calculations and designs relating to    
such structures1 the results vary far   
too widely4 ,too much is left to the    
judgment of the engineer1 and too       
frequently no fixed standards can be    
found for some of the most essential    
conditions4  ,until the engineer can say
 with certainty that his calculations   
are reasonably based on facts1 he is    
forced to admit that his design must be 
lacking1 either in the elements of      
safety1 on the one hand1 or of economy1 
on the other1 and1 until he can give to 
his client a full measure of both these 
factors in fair proportion1 he cannot   
justly claim that his profession has    
reached its full development4  ,table #a
 gives approximate calculations of      
pressures on two types of tunnels and on
 two heights of sheeted faces or walls1 
due to four varying classes of          
materials4  ,,table #a4--,,pressures    
,,on ,,typical ,,structures ,,under     
,,varying ,,assumed ,,conditions4       
,illustration3 ,key to ,table of        

,pressures1 etc4  h  exterior height1 l 
exterior width1       delta  depth of   
cover1 that is1      ,d,e  earth1 and   
,d,w  water depth1  phi  angle of       
repose1 and1 for tunnels ,d,w  ,d,e a   
depth         l           phi      -----
 7 #de  ------- 7         #b            
#b  ,w,e  weight of #a cu4 ft4 of earth 
#ij lb42 ,w,w  weight of #a cu4 ft4 of  
water  #fb lb4  ,conditions3 #a  normal 
sand1 #b  dry sand1 #c  supersaturated  
firm sand with #dj of voids1 #d         
supersaturated semi-aqueous material1   
#fj aqueous1 that is1 #fj water and     
aqueous material4                       
,combined                               
assumed     h     l    phi     ,d,e     
conditions4                             
,i#a       #bj      #cj      #de        
#dj           ,i#b       #bj      #cj   
#cj       #dj          ,,ii#a       #ae 
#ae      #de       #dj          ,,ii#b  
#ae      #ae      #cj       #dj         
,,iii#a       #ae              #de      
#ae         ,,iii#b       #ae           

#cj       #ae          ,,iv#a       #cj 
#de       #cj          ,,iv#b       #cj 
#cj       #cj                           
,combined                               
assumed     h     l    phi    ,d,e      
,d,w     conditions4                    
,i#c       #bj      #cj      #ej        
#dj          #fj           ,i#d         
#bj      #cj      #dj       #dj         
#fj          ,,ii#c       #ae      #ae  
#ej       #dj          #fj              
,,ii#d       #ae      #ae      #dj      
#dj          #fj         ,,iii#c        
#ae              #ej       #ae          
#ae         ,,iii#d       #ae           
#dj       #ae          #ae              
,,iv#c       #cj              #ej       
#cj          #cj          ,,iv#d        
#cj              #dj       #cj          
#cj         ,,approximate ,,pressures   
,,on ,,tunnels1 ,,per ,,square ,,foot4  
,pressure   ,i#a ,i#c ,i#c ,i#c    ,i#b 
,i#d ,i#d ,i#d per                      
square,earth4,earth4,water4,combined4,ea
rth4,earth4,water4,combined4 foot1 at   

,a         #c1bdj #c1fij #a1ejj   #e1aij
  #b1cbe #b1hhj #b1bej #e1acj  ,b       
#b1gde #c1aje #a1ejj   #d1fje  #a1hde   
#b1che #b1bej #d1fce  ,c         #b1afj 
#b1dge #a1ejj   #c1ige  #a1cej #a1hjj   
#b1bej #d1jej  ,d           #dej   #edj 
#a1ejj   #b1jdj    #dej   #dej #b1bej   
#b1gjj  ,e           #cfj   #cfj #a1fbe 
#a1ihe    #dej   #dej #b1dch #b1hhh  ,f 
#bgj   #bgj #a1gej   #b1jbe    #dej     
#cfj #b1fbf #b1ihf  ,g           #bbe   
#bbe #a1hge   #b1ajj    #cfj   #bgj     
#b1had #c1jhd                           
,pressure  ,,ii#a;,,ii#c;,,ii#c;,,ii#c  
,,ii#b;,,ii#d;,,ii#d;,,ii#d per         
square,earth4,earth4,water4,combined4,ea
rth4,earth4,water4,combined4 foot at    
,a         #a1dhe #a1gee #a1ejj   #c1bee
  #a1jce #a1cje #b1bej #c1eee  ,b       
#a1cje #a1dhe #a1ejj   #b1ihe    #ide   
#a1agj #b1bej #c1dbj  ,c         #a1abe 
#a1bae #a1ejj   #b1gae    #haj   #iij   
#b1bej #c1bdj  ,d           #dje   #dje 
#a1ejj   #a1ije    #edj   #dej #b1bej   
#b1gjj  ,e           #dje   #dje #a1fbe 

#b1jcj    #edj   #dej #b1dch #b1hhh  ,f 
#cfj   #cfj #a1gej   #b1aaj    #edj     
#dej #b1fbf #c1jgf  ,g           #cae   
#cae #a1hge   #b1aij    #cfj   #cfj     
#b1had #c1agd  ,h           #ahj   #bbe 
#b1jjj   #b1bbe    #ahj   #ahj #c1jjj   
#c1ahj  ,i            #ij   #aaj #b1age 
#b1bhe    #ace   #ace #c1ahh #c1cbc     
,,approximate ,,pressures ,,on ,,sheeted
 ,,trench ,,faces ,,or ,,walls          
,pressure                               
,,iii#a;,,iii#c;,,iii#c;,,iii#c;,,iii#b;
,,iii#d;,,iii#d;,,iii#d per             
square,earth4 ,earth4 ,water4  ,total   
,earth4 ,earth4 ,water4  ,total foot at 
earth                       earth       
and                         and         
water4                      water4      
,a          #ege    #eaj    #ajj    #faj
   #a1cej   #haj    #adj    #iej  ,b    
#djj    #cej    #aij    #edj     #ijj   
#edj    #bfj    #hjj  ,c          #bjj  
#age    #bhj    #dee     #dej   #bgj    
#chj    #fej                            
,pressure                               

,,iv#a;,,iv#c;,,iv#c;,,iv#c;,,iv#b;,,iv#
d;,,iv#d;,,iv#d per                     
square,earth4,earth4,water4,total       
,earth4,earth4,water4,total foot at     
earth                   earth           
and                     and             
water4                  water4          
,a         #a1cgj #a1baj  #ajj  #a1caj  
#c1age #a1iaj   #aej #b1jfj  ,b         
#a1agj #a1jcj  #bjj  #a1bcj #b1gjj      
#a1faj   #bij #a1ijj  ,c           #igj 
#hee  #bij  #a1ade #b1bej #a1cee   #dcj 
#a1ghe  ,d           #gge   #fhj  #cgj  
#a1jej #a1hjj #a1ajj   #egj #a1fgj  ,e  
#eij   #eae  #dfj    #ige #a1cej   #hbj 
#gaj #a1ecj  ,f           #djj   #cej   
#efj    #iaj   #ijj   #edj   #hfj #a1djj
  ,g           #aij   #agj  #fej    #hbj
   #dej   #bge #a1jjj #a1bge            
,,footnotes3  ,footnote ,a3 ,presented  
at the meeting of ,may #ahth1 #aiaj4    
,footnote ,b3 ,transactions1 ,am4 ,soc4 
,c4 ,e41 ,vol4 ,,lx1 p4 #a4  ,footnote  
,c3 ,engineering ,news1 ,july #ast1     
#aiji4  ,footnote ,d3 ,from ,gravel for 

,good ,roads4  ,footnote ,e3            
,transactions1 ,am4 ,soc4 ,c4 ,e41 ,vol4
 ,,lxviii1 pp4 #eh-fj4  ,footnote ,f3   
,discoveries and ,inventions of the     
,nineteenth ,century1 by ,robert        
,routledge1 ,assistant ,examiner in     
,chemistry and in ,natural ,philosophy  
to the ,university of ,london4          
,footnote ,g3 ,engineering ,news1       
,january #aeth1 #aiji4     ,,discussion 
,t4 ,,kennard ,,thomson1 ,m4 ,,am4      
,,soc4 ,c4 ,e4--,although the author    
deserves great credit for the careful   
and thorough manner in which he has     
handled this subject1 his paper should  
be labeled ,dangerous for ,beginners1   
especially as he is an engineer of great
 practical experience2 if he were not1  
comparatively little attention would be 
paid to his statements4 ,the paper is   
dangerous because many will read only   
portions of it1 or will not read it     
thoroughly4 ,for instance1 at the       
beginning1 the author cites several     
experiments in which considerable force 

is required to start the lifting of a   
weight or plunger in sand and water and 
much less after the start4 ,this reminds
 the speaker of the time when1 as a     
schoolboy1 he tried to pick up stones   
from the bottom of the river and was    
told that the suction was caused by     
atmospheric pressure4  ,the inference is
 that tunnels1 etc41 in sand1 etc41 are 
not in any danger of rising1 even though
 they are lighter than water4 ,toward   
the end of the paper1 however1 the      
author states that tunnels should be    
weighted1 but he rather spoils this by  
stating that they should be weighted    
only enough to overcome the actual water
 pressure1 that is1 between the voids of
 the sand4 ,it seems to the speaker that
 the only really safe way is to make the
 tunnel at least as heavy as the water  
displaced in order to prevent it from   
coming up1 and to take other measures to
 prevent it from going down4 ,the ,city 
of ,toronto1 ,canada1 formerly pumped   
its water supply through a #f-;ft4 iron 

pipe1 buried in the sand under ,toronto 
,bay and then under ,toronto ,island1   
with an intake in the deep water of the 
lake4 ,during a storm a mass of seaweed1
 etc41 was washed against the intake1   
completely blocking it1 and although the
 man at the pumping station knew that   
something was wrong1 he continued to    
pump until the water was drawn out of   
the pipe1 with the result that about    
half a mile of the conduit started to   
rise and then broke at several places1  
thus allowing it to fill with water4    
,eventually1 the city went down to      
bed-rock under the ,bay for its water   
tunnel4  ,another reason for calling    
this paper dangerous for beginners is   
that it is improbable that experienced  
engineers or contractors will omit the  
bracing at the bottom1 although1 since  
the paper was printed1 a glaring        
instance has occurred where             
comparatively little bracing was put in 
the bottom of a #dj-;ft4 cut1 the result
 being a bad cave-in from the bottom1   

although all the top braces remained in 
place4 ,most engineers will agree that  
nearly every crib which has failed      
slipped out from the bottom1 and did not
 turn over4  ,the objection to the angle
 of repose is that it is not possible to
 ascertain it for any material deposited
 by ,nature4 ,it could probably be      
ascertained for a sand bank deposited by
 ,man1 but not for an excavation to be  
made in the ground1 for it is known that
 nearly all earth1 etc41 has been       
deposited under great pressure1 and is  
likely to be cemented together by clay1 
loam1 roots1 trees1 boulders1 etc41 and 
differs in character every few feet4  ,a
 deep vertical cut can often be made1   
even in ,new ,york quicksand1 from which
 the water has been drawn1 and1 if not  
subjected to jars1 water1 etc41 this    
material will stand for considerable    
time and then come down like an         
avalanche1 killing any one in its way4  
,in such cases very little bracing would
 prevent the slide from starting1       

provided rain1 etc41 did not loosen the 
material4  ,the author1 of course1      
treats dry and wet materials            
differently1 but there are very few     
places where dry material is not likely 
to become wet before the excavation is  
completed4  ,in caisson work1 if the    
caisson can be kept absolutely plumb1 it
 can be sunk without having to overcome 
much friction1 while1 on the other hand1
 if it is not kept plumb1 the material  
is more or less disturbed and begins to 
bind1 causing considerable friction4    
,the author claims that the pressure    
does not increase with the depth1 but   
all caisson men will probably remember  
that the friction to be overcome per    
square foot of surface increases with   
the depth4  ,in calculating retaining   
walls1 many engineers add the weight of 
the soil to the water1 and calculate for
 from #ij to #ajj lb4 per cu4 ft4 ,the  
speaker is satisfied that in the        
so-called ,new ,york quicksand it is    
sufficient to use the weight of the     

water only4 ,if the sand increased the  
side pressure above the water pressure1 
engineers would expect to use more      
compressed air to hold it back1 while1  
as a matter of fact1 the air pressure   
used seldom varies much from that called
 for by the hydrostatic head4  ,although
 allowance for water pressure is        
sufficient for designing retaining walls
 in ,new ,york quicksand1 it is far from
 sufficient in certain silty materials4 
,for instance1 in ,maryland1 a          
coffer-dam1 excavated to a depth of #cj 
ft4 in silt and water1 had the bottom   
shoved in #b ft41 in spite of the fact  
that the waling pieces were #e ft4 apart
 vertically at the top and #c ft4 at the
 bottom1 and were braced with #ab by    
#ab-;in4 timbers1 every #g ft4          
horizontally4 ,the walings split1 and   
the cross-braces cut into the waling    
pieces from #a to #b in42 in other      
words1 the pressure seemed to be almost 
irresistible4 ,this is quite a contrast 
to certain excavations in ,brooklyn1    

which1 without any bracing whatever1    
were safely carried down #ae ft4  ,any  
engineer who tries to guess at the angle
 of repose1 and1 from the resulting     
calculations1 economizes on his bottom  
struts1 will find that sooner or later  
an accident on one job will cause enough
 loss of life and money to pay for      
conservative timbers for the rest of his
 life4 ,so much for side pressures4 ,as 
to the pressure in the roof of a tunnel1
 probably every engineer will agree that
 almost any material except unfrozen    
water will tend to arch more or less1   
but how much it is impossible to say4   
,it is doubtful whether any experienced 
engineer would ever try to carry all the
 weight over the roof1 except in the    
case of back-fill1 and even then he     
would have to make his own assumption   
7which sounds more polite than guess74  
,the author has stated1 however1 that   
when the tunnel roof and sides are in   
place1 no further trouble need be       
feared4 ,on the contrary1 in #ahhe1 the 

,canadian ,pacific ,railroad built a    
tunnel through clayey material and lined
 it with ordinary #ab by #ab-;in4 timber
 framing1 about #b or #c ft4 apart4     
,after the tunnel was completed1 it     
collapsed4 ,it was re-excavated and     
lined with #ab by #ab-;in4 timbers side 
by side1 and it collapsed again2 then   
the tunnel was abandoned1 and1 for some 
#bj years1 the track1 carried around on 
a #bc curve1 was used until a new tunnel
 was built farther in4 ,this trouble    
could have been caused either by the    
sliding or swelling of the material1 and
 the speaker is inclined to believe that
 it was caused by swelling1 for it is   
known1 of course1 that most material has
 been deposited by ,nature under great  
pressure1 and1 by excavating in certain 
materials1 the air and moisture would   
cause those materials to swell and      
become an irresistible force4  ,to carry
 the load1 ,mr4 ,meem prefers to rely on
 the points of the piles rather than the
 side friction4 ,in such cases the pile 

would act as a post1 and would probably 
fail when ordinarily loaded1 unless     
firmly supported at the sides4 ,the     
speaker has seen piles driven from #hj  
to #ij ft4 in #aj min41 which offered   
almost no resistance1 and yet1 a few    
days later1 they would sustain #dj tons 
each4 ,no one would dream of putting #dj
 tons on a #ij-;ft4 pile resting on     
rock1 if it were not adequately         
supported4  ,it is the speaker's opinion
 that bracing should not be omitted for 
either piles or coffer-dams4   ,,charles
 ,e4 ,,gregory1 ,,assoc4 ,m4 ,,am4      
,,soc4 ,c4 ,e4--,in describing his last 
experiment with the hydraulic chambers  
and plunger1 ,mr4 ,meem states that1    
after letting the pressure stand at #be 
lb41 etc41 the piston came up4 ,this    
suggests that the piston might have been
 raised at a much lower pressure1 if it 
had been allowed to stand long enough4  
,the depth and coarseness of the sand   
were not varied to ascertain whether any
 relation exists between them and the   

pressure required to lift the piston4   
,if the pressure varied with the depth  
of sand1 it would indicate that the     
reduction was due to the resistance of  
the water when finely divided by the    
sand2 if it varied with the coarseness  
of the sand1 as it undoubtedly would1   
especially if the sand grains were      
increased to spheres #a in4 in diameter1
 it would show that it was independent  
of the voids in the sand1 but dependent 
on dividing the water into thin films4  
,the speaker believes that the greater  
part of the reduction of pressure on the
 bottom of the piston might be better   
explained by the viscosity of the water1
 than to assume that a considerable part
 of the plunger is not in contact with  
it4 ,the water1 being divided by fine   
sand into very thin films1 has a tensile
 strength which is capable of resisting 
the pressure for at least a limited     
time4  ,if the water is capable of      
exerting its full hydrostatic pressure  
through the sand1 the total pressure    

would be the full hydrostatic pressure  
on the bottom of the piston where in    
contact1 and1 where separated from it by
 a grain of sand1 the pressure would be 
decreased only by the weight of the     
grain4 ,if a large proportion of the top
 area of a grain is in contact1 as      
assumed by the author1 this reduction of
 pressure would be very small4 ,a       
correct interpretation can be obtained  
only after more complete experiments    
have been made4  ,for horizontal        
pressures exerted by saturated sands on 
vertical walls1 it has not been         
demonstrated that anything should be    
deducted from full water pressure4 ,no  
matter how much of the area is in direct
 contact with the sand rather than the  
water1 the full water pressure would be 
transmitted through each sand grain from
 its other side and1 if necessary1 from 
and through many other grains which may 
be in turn in contact with it4 ,the     
pressure on such a wall will be water   
pressure over its entire surface1 and1  

in addition1 the thrust of the sand     
after correcting for its loss of weight 
in the water4  ,the fact that small     
cavities may be excavated from the sides
 of trenches or tunnels back of the     
sheeting proves only that there is a    
local temporary arching of the material1
 or that the cohesion of the particles  
is sufficient to withstand the stress   
temporarily1 or that there is a         
combination of cohesion and arching4    
,the possibility of making such         
excavations does not prove that pressure
 does not exist at such points4 ,that   
sand or earth will arch under certain   
conditions has long been an accepted    
fact4 ,the sand arches experimented with
 developed their strength only after    
considerable yielding and1 therefore1   
give no index of the distribution or    
intensity of stress before such         
yielding4 ,furthermore1 sand and earth  
in ,nature are not constrained by forms 
and reinforcing rods4  ,mr4 ,meem's     
paper is very valuable in that it       

presents some unusual phenomena1 but    
many of the conclusions drawn therefrom 
cannot be accepted without further      
demonstration4   ,,francis ,w4 ,,perry1 
,,assoc4 ,m4 ,,am4 ,,soc4 ,c4           
,e4--,pressure-gauge observations on a  
number of pneumatic caissons recently   
sunk1 through various grades of sand1 to
 rock at depths of from #he to #aje ft4 
below ground-water1 invariably showed   
working-chamber air-pressures equal1 as 
closely as could be observed1 to the    
hydrostatic pressures computed1 for     
corresponding depths of cutting-edge1 as
 given in ,table #b4  ,these            
observations and computations were made 
by the speaker in connection with the   
caisson foundations for the ,municipal  
,building1 ,new ,york ,city4   ,,table  
#b4--;,,equivalent ,,feet ,,of ,,depth  
,,below ,,water ,,per ,,pound           
,,pressure4  ,pressure1 ,equivalent     
,equivalent   ,observed       in        
feet of    elevation    pressure4       
pounds4   depth4     for water          

at--#f4he4                              
,m4,h4,w4     ,ground-water4            
#a         #b4ca       #i4jf            
,practically      #b         #d4fc      
#aa4dh       the same as      #c        
#f4id      #ac4gi       computed        
#d         #i4be      #af4aj       for  
#e        #aa4eg      #ah4db            
ground-water4    #f        #ac4hh       
#bj4gc                        #g        
#af4ai      #bc4jd                      
#h        #ah4ej      #be4ce            
#i        #bj4hb      #bg4fg            
#aj        #bc4ac      #bi4ih           
#aa        #be4dd      #cb4bi           
#ab        #bg4gf      #cd4fa           
#ac        #cj4jg      #cf4ib           
#ad        #cb4ch      #ci4bc           
#ae        #cd4gj      #da4ee           
#af        #cg4ja      #dc4hf           
#ag        #ci4cb      #df4ag           
#ah        #da4fc      #dh4dh           
#ai        #dc4ie      #ej4hj           
#bj        #df4bf      #ec4aa           
#ba        #dh4eg      #ee4db           

#bb        #ej4hi      #eg4gd           
#bc        #ec4bj      #fj4je           
#bd        #ee4ea      #fb4cf           
#be        #eg4hb      #fd4fg           
#bf        #fj4ad      #ff4ii           
#bg        #fb4de      #fi4cj           
#bh        #fd4gf      #ga4fa           
#bi        #fg4jh      #gc4ic           
#cj        #fi4ci      #gf4bd           
#ca        #ga4gj      #gh4ee           
#cb        #gd4ja      #hj4hf           
#cc        #gf4cc      #hc4ah           
#cd        #gh4fd      #he4di           
#ce        #hj4ie      #hg4hj           
#cf        #hc4bg      #ij4ab           
#cg        #he4eh      #ib4dc           
#ch        #hg4hi      #id4gd           
#ci        #ij4bj      #ig4je           
#dj        #ib4eb      #ii4cg           
#da        #id4hc     #aja4fh           
#db        #ig4ad     #ajc4ii           
#dc        #ii4df     #ajf4ca           
#dd       #aja4gg     #ajh4fb           
#de       #ajd4jh     #aaj4ic           
#df       #ajf4ci     #aac4bd           

#cd ,,note4--,equivalent depth in feet  
------  pressure4                       
#ad4g   ,e4,p4 ,,goodrich1 ,m4 ,,am4    
,,soc4 ,c4 ,e4 7by letter74--,this paper
 is to be characterized by superlatives4
 ,parts of it are believed to be        
exceptionally good1 while other parts   
are considered equally dangerous4 ,the  
author's experimental work is extremely 
interesting1 and the writer believes the
 results obtained to be of great value2 
but the analytical work1 both           
mathematical and logical1 is            
emphatically questioned4  ,the writer   
believes that1 in the design of         
permanent structures1 consideration of  
arch action should not be included1 at  
least1 not until much more information  
has been obtained4 ,he also believes    
that the design of temporary structures 
with this inclusion is actually         
dangerous in some instances1 and takes  
the liberty of citing the following     
statement by the author1 with regard to 
his first experiment3       ,about an   

hour after the superimposed load had    
been removed1 the      writer jostled   
the box with his foot sufficiently to   
dislodge some      of the exposed sand1 
when the arch at once collapsed and the 
bottom      fell to the ground4  ,the   
writer emphatically questions the       
author's ideas as to the thickness of   
key which should be allowed over        
tunnels1 believing that conditions      
within an earth mass1 except in very    
rare instances1 are such that true arch 
action will seldom take place to any    
definite extent1 through any            
considerable depths4 ,furthermore1 the  
author's reason for bisecting the angle 
between the vertical and the angle of   
repose of the material1 when he         
undertakes to determine the thickness of
 key1 is not obvious4 ,this assumption  
is shown to be absurd when carried to   
either limit1 for when the angle of     
repose equals zero1 as is the case with 
water1 this1 method would give a        
definite thickness of key1 while there  

can be absolutely no arch action        
possible in such a case2 and1 when the  
angle of repose is #ij1 as may be       
assumed in the case of rock1 this method
 would give an infinite thickness of    
key1 which is again seen to be absurd4  
,it would seem as if altogether too many
 unknowable conditions had been assumed4
 ,in any case1 no arch action can be    
brought into play until a certain amount
 of settlement has taken place so as to 
bring the particles into closer contact1
 and in such a way that the internal    
stresses are practically those only of  
compression1 and the shearing stresses  
are within the limits possible for the  
material in question4  ,the author has  
repeatedly made assumptions which are   
not borne out by the application of his 
mathematical formulas to actual extreme 
conditions4 ,this method of application 
to limiting conditions is concededly    
sometimes faulty2 but the writer        
believes that no earth pressure theory1 
or one concerning arch action1 can be   

considered as satisfactory which does   
not apply equally well to hydraulic     
pressure problems when the proper       
assumptions are made as to the factors  
for friction1 cohesion1 etc4 ,for       
example1 when the angle of repose is    
considered as zero1 in the author's     
first formula for ,w#a1 the value       
becomes  ,w#a1 whereas it should depend 
solely on the depth1 which does not     
enter the formula1 and not at all on the
 width of opening1 l1 which is thus     
included4  ,the author has given no     
experiments to prove his statement that 
the arch thrust is greater in dryer     
sand1 and the accuracy of the statement 
is questioned4 ,again1 no reason is     
apparent for assuming the direction of  
the rakers in ,fig4 #c as that of the   
angle of repose4 ,the writer cannot see 
why that particular angle is repeatedly 
used1 when almost any other would give  
results of a similar kind4 ,the author  
has made no experiments which show any  
connection between the angle of repose1 

as he interprets it1 and the lines of   
arch action which he assumes to exist4  
,with regard to the illustration of the 
condition which is thought to exist when
 the material is composed of large      
bowling balls1 supposedly all of the    
same size1 the writer believes the      
conclusion to be erroneous1 and that    
this can be readily seen by inspection  
of a diagram in which such balls are    
represented as forming a pile similar to
 the well-known pile of shells of the   
algebras1 in the diagram of which a pile
 of three shells1 resting on the base1  
has been omitted4 ,it is then seen that 
unless the pressures at an angle of #fj 
with the horizontal are sufficient to   
produce frictional resistance of a very 
large amount1 the balls will roll and   
instantly break the arch action         
suggested by the author4 ,consequently1 
an almost infinitesimal settlement of   
the centering may cause the complete    
destruction of an arch of earth4  ,the  
author's logic is believed to be        

entirely faulty in many cases because he
 repeatedly makes assumptions which are 
not in accordance with demonstrated     
fact1 and finally sums up the results by
 the statement3 ,it is conceded 7line   
#b1 p4 #ceg1 for example71 when the     
writer1 for one1 has not even conceded  
the accuracy of the assumptions4 ,for   
instance1 the author's well-known theory
 that pressures against retaining walls 
are a maximum at the top and decrease to
 zero at the bottom1 is in absolute     
contradiction to the results of         
experiments conducted on a large scale  
by the writer on the new reinforced     
concrete retaining wall near the ,st4   
,george ,ferry1 on ,staten ,island1 ,new
 ,york ,city1 which will soon be        
published1 and in which the usual law of
 increase of lateral pressure with depth
 is believed to be demonstrated beyond  
question4 ,it must be conceded that a   
considerable arch action 7so-called7    
actually exists in many cases2 but it   
should be equally conceded by the       

advocates of the existence of such      
action that changes in humidity1 due to 
moving water1 vibration1 and appreciable
 viscosity1 etc41 will invariably       
destroy this action in time4 ,in        
consequence1 the author's reasoning in  
regard to the pressures against the     
faces of retaining walls is believed to 
be open to grave question as to accuracy
 of assumption1 method1 and conclusion4 
,the author is correct in so far as he  
assumes that the character of the       
stresses due to the thrust of the       
material will not change if bracing     
should be substituted for the material  
in the area designated by him1 etc41    
provided he makes the further assumption
 that absolutely no motion1 however     
infinitesimal1 has taken place meantime2
 but1 unless such motion has actually   
taken place1 no arch action can have    
developed4 ,an arch thrust can result   
only with true arch action1 that is1    
with stable abutments1 and the mass     
stressed wholly in compression1 with    

corresponding shortening of the arch    
line4 ,the arch thrust must be          
proportional to the elastic deformation 
7shortening7 of the arch line4 ,if any  
such arch as is shown in ,fig4 #e is    
assumed to carry the whole of the weight
 of material above it1 that assumed arch
 must relieve all the assumed arches    
below4 ,therefore each of the assumed   
arches can carry nothing more than its  
own mass4 ,otherwise the resulting      
thrust would increase with the depth1   
which is opposed to the author's theory4
  ,turning again to the condition that  
each arch can carry only its own weight3
 if these arches are assumed of         
thicknesses proportional to the distance
 upward from the bottom of the wall1    
they will be similar figures1 and it is 
easily demonstrated that the thrust will
 then be uniform in amount throughout   
the whole height of the wall1 except1   
perhaps1 at the very top4 ,this         
condition is contrary to the author's   
ideas and also to the facts as          

demonstrated by the writer's experiment 
on the #dj-;ft4 retaining wall at ,st4  
,george4 ,consequently1 the author's    
statement3 nor can anyone 99 99 99 doubt
 that the top timbers are stressed more 
heavily than those at the bottom1 is    
emphatically doubted and earnestly      
denied by the writer4 ,furthermore1 the 
assumption made by the author as to the 
tendency of the material to slide so as 
to cause it to wedge 99 99 99 between   
the face of the sheeting 99 99 99 and   
some plane between the sheeting and the 
plane of repose1 is considered as       
absolutely unwarranted1 and consequently
 the whole conclusion is believed to be 
unjustified4 ,nor is the author's       
assumption 7line #e1 p4 #cfa71 that the 
thrust 99 99 99 is measured by its      
weight divided by the tangent of the 99 
99 99 angle of repose at all obvious4   
,the author presents some very          
interesting photographs showing the     
natural surface slopes of various       
materials2 but it is interesting to note

 that he describes these slopes as      
having been produced by the continual   
slipping down of particles4 ,the vast   
difference between angles of repose     
produced in this manner by the rolling  
friction of particles and the internal  
angles of friction1 which must be used  
in all earth-pressure investigations1   
has been repeatedly called to the       
attention of engineers by the writer4,h 
,the writer's experiments are entirely  
in accord with those of the author in   
which the latter claims to demonstrate  
that earth and water pressures act      
independently of each other1 and the    
writer is much delighted that his own   
experiments have been thus confirmed4   
,in ,experiment ,no4 #c1 the query is   
naturally suggested3 ,what would have   
been the result if the nuts and washers 
had first been tightened and water then 
added8 ,although the writer has not     
tried the experiment1 he is rather      
inclined to the idea that the arch would
 have collapsed4 ,with regard to        

,experiment ,no4 #e1 there is to be     
noted an interesting possibility of its 
application to the theoretical          
discussion of masonry dams1 in which    
films of water are assumed to exist     
beneath the structure or in crevices or 
cracks of capillary dimensions4 ,the    
writer has always considered the        
assumptions made by many designing      
engineers as unnecessarily conservative4
 ,in regard to the author's conclusions 
from ,experiment ,no4 #f1 it should be  
noted that no friction can exist between
 particles of sand and surrounding water
 unless there is a tendency of the      
latter to move2 and that water in motion
 does not exert pressures equal to those
 produced when in a static condition1   
the reduction being proportional to the 
velocity of flow4  ,the author's        
conclusion 7p4 #cga71 that pressure will
 cause the quicksand to set up hydraulic
 action1 does not seem to have been     
demonstrated by his experiments1 but to 
be only his theory4 ,in this instance1  

the results of the writer's experiments 
are contrary to the author's theory and 
conclusion4  ,the writer will heartily  
add his protest to that of the author   
against considering semi-aqueous masses1
 such as soupy sands1 soft concrete1    
etc41 as exerting hydrostatic pressure  
due to their weight in bulk1 instead of 
to the specific gravity of the basic    
liquid4 ,again1 similarly hearty        
concurrence is given to the author's    
statement3       ,if the solid material 
in any liquid is agitated1 so that it is
      virtually in suspension1 it cannot
 add to the pressure1 and if            
allowed to subside it acts as a solid1  
independently of the water              
contained with it1 although the water   
may change somewhat the      properties 
of the material1 by increasing or       
changing its cohesion1      angle of    
repose1 etc4  ,on the other hand1 it is 
believed that the author's statement1 as
 to the tendency of marbles to arch1 a  
few lines above the one last quoted1    

should be qualified by the addition of  
the words1 only when a certain amount of
 deflection has taken place so as to    
bring the arch into action4 ,again1 on  
the following page1 a somewhat similar  
qualification should be added to the    
sentence referring to the soft clay     
arch1 that it would stand if the rods   
supporting the intrados of the arch were
 keyed back to washers covering a       
sufficiently large area1 by inserting   
the words1 unless creeping pressures    
7such as those encountered by the writer
 in his experiments7 were exceeded4     
,the writer considers as very doubtful  
the formula for ,dx1 which is the same  
as that for ,w#a1 already discussed4    
,the author's statement that additional 
back-fill will under certain            
circumstances lighten the load on the   
structure1 is considered subject to     
modification by some such clause as the 
following1 the word 'lighten' here being
 understood to mean the reduction to    
some extent of what would be the total  

pressure due to the combined original   
and added back-fill1 provided no arch   
action occurred4  ,the writer is in     
entire agreement with the author as to  
the probability that water is often cut 
off absolutely from its source of       
pressure1 with the attendant results    
described by the author 7p4 #cgh72 and  
again1 that too little attention has    
been given to the bearing power of soil1
 with the author's accompanying         
criticism4  ,the writer cannot see1     
however1 where the author's experiments 
demonstrate his statement that pressure 
is transmitted laterally through ground1
 most probably along or nearly parallel 
to the angles of repose1 or any of the  
conclusions drawn by him in the         
paragraph 7p4 #cha71 which contains this
 questionable statement4 ,again the     
writer is at a loss as to how to        
interpret the statement that the author 
has found that better resistance has    
been offered by small open caissons sunk
 to a depth of a few feet and cleaned   

out and filled with concrete than by    
spreading the foundation over four or   
five times the equivalent area4 ,the    
writer agrees with the author in the    
majority of his statements as to the    
bearing value and friction on piles1 but
 believes that he is indulging in pure  
theory in some of his succeeding        
remarks1 wherein he ascribes to arch    
action the results which he believes    
would be observed if a long shaft be    
withdrawn vertically from moulding sand4
 ,these phenomena would be due rather to
 capillary action and the resulting     
cohesion4  ,naturally1 the writer doubts
 the author's conclusions as to the     
pressure at the top of large square     
caisson shafts when he states that the  
pressure at the top 99 99 99 will 99 99 
99 increase proportionately to the      
depth4 ,again1 the author is apparently 
not conversant with experiments made by 
the ,dock ,department of ,new ,york     
,city1 concerning piles driven in the   
,hudson ,river silt1 which showed that a

 single heavily loaded pile carried     
downward with it other unloaded piles1  
driven considerable distances away1     
showing that it was not the pile which  
lacked in resistance1 as much as the    
surrounding earth4  ,in conclusion1 the 
writer heartily concurs with the        
statement that too much has been taken  
for granted in connection with earth    
pressures and resistance1 and he is     
sorry to be forced to add that he       
believes the author to be open to the   
criticism which he himself suggests1    
that both in experimenting and          
observing1 the engineer and in this case
 the author will frequently find what is
 being looked for or expected and will  
fail to see the obvious alternative4    
,,francis ,l4 ,,pruyn1 ,m4 ,,am4 ,,soc4 
,c4 ,e4 7by letter74--,mr4 ,meem should 
be congratulated1 both in regard to the 
highly interesting theories which he    
advances on the subject of sand         
pressures--the pressures of subaqueous  
material--and on his interesting        

experiments in connection therewith4    
,the experiment in which the plunger on 
the hydraulic ram is immersed in sand   
and covered with water does not seem to 
be conclusive4 ,by this experiment the  
author attempts to demonstrate that the 
pressure of the water transmitted       
through the sand is only about #dj as   
great as when the sand is not there4    
,the travel of ground-water through the 
earth is at times very slow1 and        
occasionally only at the rate of from #b
 to #c ft4 per hour4 ,in the writer's   
opinion1 ,mr4 ,meem's experiment did not
 cover sufficient time during which the 
pressure was maintained at any given    
point4 ,it is quite probable that it may
 take #ae or #bj min4 for the full      
pressure to be transmitted through the  
sand to the bottom of the plunger1 and  
it is hoped1 therefore1 that he will    
make further experiments lasting long   
enough to demonstrate this point4  ,in  
regard to the question of skin friction 
on caissons and piles1 it may be of     

interest to mention an experiment which 
the writer made during the sinking of   
the large caissons for the ,williamsburg
 ,bridge4 ,these caissons were about #gj
 ft4 long and #ej ft4 wide4 ,the river  
bottom was about #ej ft4 below mean high
 water1 and the caissons penetrated sand
 of good quality to a depth of from #ij 
to #ajj ft4 below that level4 ,on two   
occasions calculations were made to     
determine the skin friction while the   
caissons were being settled4 ,with the  
cutting edge from #bj to #cj ft4 below  
the river bottom1 the calculations      
showed that the skin friction was       
between #ejj and #fjj lb4 per sq4 ft4   
,the writer agrees with ,mr4 ,meem that1
 in the sinking of caissons1 the arch   
action of sand is1 in a great measure1  
destroyed by the compressed air which   
escapes under the cutting edge and      
percolates up through the material close
 to the sides of the caissons4  ,with   
reference to the skin friction on piles1
 the writer agrees with ,mr4 ,meem that 

in certain classes of material this is  
almost a negligible quantity4 ,the      
writer has jacked down #i-;in4 pipes in 
various parts of ,new ,york ,city1 and  
by placing a recording gauge on the     
hydraulic jack1 the skin friction on the
 pile could be obtained very accurately4
 ,in several instances the gauge        
readings did not vary materially from   
the surface down to a penetration of #ej
 ft4 ,in these instances the material   
inside the pipe was cleaned out to      
within #a ft4 of the bottom of the pile1
 so that the gauge reading indicated    
only the friction on the outside of the 
pipe plus the bearing value developed by
 its lower edge4 ,for a #i-;in4 pipe1   
the skin friction on the pile plus the  
bearing area of the bottom of the pipe  
seems to be about #bj tons1 irrespective
 of the depth4 ,after the pipe had      
reached sufficient depth1 it was        
concreted1 and1 after the concrete had  
set1 the jack was again placed on it and
 gauge readings were taken4 ,it was     

found that in ordinary sands the        
concreted steel pile would go down from 
#c to #f in41 after which it would bring
 up to the full capacity of a #fj-ton   
jack1 showing1 by gauge reading1 a      
reaction of from #gj to #hj tons4  ,it  
is the writer's opinion that1 in        
reasonably compact sands situated at a  
depth below the surface which will not  
allow of much lateral movement1 a       
reaction of #ajj tons per sq4 ft4 of    
area can be obtained without any        
difficulty whatever4   ,,frank ,h4      
,,carter1 ,,assoc4 ,m4 ,,am4 ,,soc4 ,c4 
,e4 7by letter74--,mr4 ,meem has        
contributed much that is of value1      
particularly on water pressures in sand2
 just what result would be obtained if  
coarse crushed stone or similar material
 were substituted for sand in           
,experiment ,no4 #f1 is not obvious4    
,it has been the practice lately1 among 
some engineers in ,boston1 as well as in
 ,new ,york ,city1 to assume that water 
pressures on the underside of inverts is

 exerted on one-half the area only4 ,the
 writer1 however1 has made it a practice
 first to lay a few inches of cracked   
stone on the bottom of wet excavations  
in order to keep water from concrete    
which is to be placed in the invert4 ,in
 addition to the cracked stone under the
 inverts1 shallow trenches dug laterally
 across the excavation to insure more   
perfect drainage1 have been observed4   
,both these factors no doubt assist the 
free course of water in exerting        
pressure on the finished invert after   
the underdrains have been closed up on  
completion of the work4 ,the writer1    
therefore1 awaits with interest the     
repetition of ,experiment ,no4 #f1 with 
water on the bottom of a piston buried  
in coarse gravel or cracked stone4  ,as 
for the arching effect of sand1 the     
writer believes that ,mr4 ,meem has     
demonstrated an important principle1 on 
a small scale4 ,it must be regretted1   
however1 that the box was not made      
larger1 for1 to the writer1 it appears  

unsafe to draw such sweeping conclusions
 from small experiments4 ,as small      
models of sailboats fail to develop     
completely laws for the design and      
control of large racing yachts1 so      
experiments in small sand boxes may fail
 to demonstrate the laws governing      
actual pressures on full-sized          
structures4  ,for some time the writer  
has been using a process of reasoning   
similar to that of the author for       
assumptions of earth pressure on the    
roofs of tunnel arches1 except that the 
vertical forces assumed to hold up the  
weight of the earth have been ascribed  
to cohesion and friction1 along what    
might be termed the sides of the trench 
excavation4  ,the writer fails to find  
proof in this paper of the author's     
statement that earth pressures on the   
sides of a structure buried in earth are
 greater at the top than at the bottom  
of a trench4 ,that some banks are       
top-heavy1 is1 no doubt1 a fact1 the    
writer having often heard similar       

expressions used by experienced trench  
foremen1 but1 in every case called to   
his attention1 local circumstances have 
caused the top-heaviness1 either        
undermining at the bottom of the trench1
 too much banked earth on top1 or the   
earth excavated from the trench being   
too near the edge of the cut4  ,for some
 years the writer has been making       
extended observations on deep trenches1 
and1 thus far1 has failed to find       
evidence1 except in aqueous material1 of
 earth pressures which might be expected
 from the known natural slope of the    
material after exposure to the elements2
 and this latter feature may explain why
 sheeted trenches stand so much better  
than expected4 ,if air had free access  
to the material1 cohesion would be      
destroyed1 and theoretical pressures    
would be more easily developed4 ,with   
closely-sheeted trenches1 weathering is 
practically excluded1 and the bracing1  
which seemingly is far too light1 holds 
up the trench with scarcely a mark of   

pressure4 ,as an instance1 in #ahic1 the
 writer was successfully digging sewer  
trenches from #aj to #ad ft4 deep1      
through gravel1 in the central part of  
,connecticut1 without bracing2 because  
of demands of the work in another part  
of the city1 a length of several hundred
 feet of trench was left open for three 
days1 resulting in the caving-in of the 
sides4 ,the elements had destroyed the  
cohesion1 and the sides of the trenches 
no longer stood vertically4  ,recently1 
in the vicinity of ,boston1 trenches1   
#cb ft4 wide1 and from #be to #ce ft4   
deep1 with heavy buildings on one side1 
have been braced with #h by #aj-;in4    
stringers1 and bracers at #aj-;ft4      
centers longitudinally1 and from #c to  
#e ft4 apart vertically2 this timbering 
apparently was too slight for pressures 
which1 theoretically1 might be expected 
from the natural slope of the material4 
,just what pressures develop on the     
sides of the structures in these deep   
trenches after pulling the top sheeting 

7the bottom sheeting being left in      
place7 is1 of course1 a matter of       
conjecture4 ,there can be no doubt that 
there is an arching of the material1 as 
suggested by the author4 ,how much this 
may be assisted by the practical        
non-disturbance of the virgin material  
is1 of course1 indeterminate4 ,that     
substructures and retaining walls       
designed according to the ,rankine or   
similar theories have an additional     
factor of safety from too generous an   
assumption in regard to earth pressure  
is practically admitted everywhere4 ,it 
is almost an engineering axiom that     
retaining walls generally fail because  
of insufficient foundation only4  ,for  
the foregoing reasons1 and particularly 
from observations on the effect of earth
 pressures on wooden timbers used as    
bracing1 the writer believes that1      
ordinarily1 the theoretical earth       
pressures computed by ,rankine and      
,coulomb are not realized by one-half1  
and sometimes not even by one-third or  

one-quarter in trenches well            
under-drained1 rapidly excavated1 and   
thoroughly braced4   ,j4,c4 ,,meem1 ,m4 
,,am4 ,,soc4 ,c4 ,e4 7by letter74--,the 
writer has been much interested in this 
discussion1 and believes that it will be
 of general value to the profession4 ,it
 is unfortunate1 however1 that several  
of the points raised have been due to a 
careless reading of1 or failure to      
understand1 the paper4  ,taking up the  
discussion in detail1 the writer will   
first answer the criticisms of ,mr4     
,goodrich4 ,he says3       ,the writer  
believes that1 in the design of         
permanent structures1      consideration
 of arch action should not be included1 
at least1 not      until more           
information has been obtained4 ,he also 
believes that the      design of        
temporary structures with this inclusion
 is actually      dangerous in some     
instances4  ,if the arching action of   
earth exists1 why should it not be      
recognized and considered8 ,the design  

of timbering for a structure to rest1   
for instance1 at a depth of from #bjj to
 #cjj ft4 in normal dry earth1 without  
considering this action1 would be       
virtually prohibitive4  ,mr4 ,goodrich  
proceeds to show one of the dangers of  
considering such action by quoting the  
writer1 as follows3       ,about an hour
 after the superimposed load had been   
removed1 the      writer jostled the box
 with his foot sufficiently to dislodge 
some      of the exposed sand1 when the 
arch at once collapsed and the bottom   
fell to the ground4  ,he fails1 as do so
 many other critics of this theory1 to  
distinguish the difference between that 
portion of the sand which acts as       
so-called centering and that which goes 
to make up the sustaining arch4 ,the    
dislodgment of any large portion of this
 centering naturally causes collapse1   
unless it is caught1 in which case the  
void in the centering is filled from the
 material in the sustaining arch1 and   
this1 in turn1 is filled from that      

above1 and so on1 until the stability of
 each arch is in turn finally           
established4 ,this1 however1 does not   
mean that1 during the process of        
establishing this equilibrium of the    
arch stresses1 there is no arching      
action of any of the material above1 but
 only that some of the so-called arches 
are temporarily sustained by those      
below4 ,that is1 in effect1 each area of
 the material above becomes1 in turn1 a 
dependent1 an independent1 and finally  
an interdependent arch4  ,if ,mr4       
,goodrich's experience has led him to   
examine any large number of tunnel      
arches or brick sewers1 he will have    
noted in many of them longitudinal      
cracks at the soffits of the arches and 
perhaps elsewhere4 ,these result from   
three causes3  ,first4--,in tunneling1  
there is more or less loss of material1 
while1 in back-filling1 the material    
does not at first reach its final       
compactness4 ,therefore1 in adjusting   
itself to normal conditions1 this       

material causes impact loads to come    
upon the green arch1 and these tend to  
crack it4  ,second4--,no matter how     
tightly a brick or other arch is keyed  
in1 there must always be some slight    
subsidence when the centers are struck4 
,this1 again1 results in a shock1 or    
impact loading1 to the detriment of the 
arch4  ,third4--,the most prolific      
cause1 however1 is that in tunneling1 as
 well as in back-filling open cuts1 the 
material backing up the haunches is more
 or less loosened and therefore is not  
at first compact enough to prevent the  
spreading of the haunches when the load 
comes on the arch4 ,this causes         
cracking1 but1 as soon as the haunches  
have been pressed out against the solid 
material1 the cracking usually ceases1  
unless the pressure has been            
sufficiently heavy to cause collapse4   
,an interesting example of this was     
noted in the ,joralemon ,street branch  
of the ,rapid ,transit ,tunnel1 in      
,brooklyn1 in which a great many of the 

cast-iron rings were cracked under the  
crown of the arch1 during construction2 
but1 in spite of this1 they sustained1  
for more than two years1 a loading      
which1 according to ,mr4 ,goodrich1 was 
continually increasing4 ,in other words1
 the cracked arch sustained a greater   
loading than that which cracked the     
plates during construction1 according to
 his theory1 as noted in the following  
quotation3       ,but it should be      
equally conceded by the advocates of the
      existence of such action that     
changes in humidity1 due to moving      
water1 vibration1 and appreciable       
viscosity1 etc41 will invariably        
destroy this action in time4  ,as to the
 correctness of this theory ,mr4        
,goodrich would probably have great     
difficulty in convincing naturalists1   
who are aware that many animals live in 
enlarged burrows the stability of which 
is dependent on the arching action of   
the earth2 in fact1 many of these       
burrows have entrances under water4 ,he 

would also have some difficulty in      
convincing those experienced miners who1
 after a cave-in1 always wait until the 
ground has settled and compacted itself 
before tunneling1 usually with apparent 
safety1 over the scene of the cave-in4  
,the writer quotes as follows from ,mr4 
,goodrich's discussion3       ,in any   
case1 no arch action can be brought into
 play until a      certain amount of    
settlement has taken place so as to     
bring the      particles into closer    
contact1 and in such a way that the     
internal      stresses are practically  
those only of compression1 and the      
shearing stresses are within the limits 
possible for the material      in       
question4  ,further3                    
,consequently1 an almost infinitesimal  
settlement of the      'centering' may  
cause the complete destruction of an    
arch of      earth4  ,and further3      
,on the other hand1 it is believed that 
the author's statement1 as      to the  
'tendency of marbles to arch1' 99 99 99 

should be qualified by      the addition
 of the words1 'only when a certain     
amount of      deflection has taken     
place so as to bring the arch into      
action4'  ,in a large measure the writer
 agrees with the first and last         
quotations1 but sees no reason to       
endorse the second1 as it is impossible 
to consider any arch being built which  
does not settle slightly1 at least1 when
 the centers are struck4  ,regarding his
 criticism of the lack of arching action
 in balls or marbles1 he seems to reason
 that the movement of the marbles would 
destroy the arch action4 ,it is very    
difficult for the writer to conceive how
 it would be possible for balls or      
marbles to move when confined as they   
would be confined if the earth were     
composed of them instead of its present 
ingredients1 and under the same         
conditions otherwise4 ,mr4 ,goodrich can
 demonstrate the correctness of the     
writer's theories1 however1 if he will  
repeat the writer's ,experiment ,no4 #c1

 with marbles1 with buckshot1 and with  
dry sand4 ,he is also advised to make   
the experiment with sand and water1     
described by the writer1 and is assured 
that1 if he will see that the washers   
are absolutely tight before putting the 
water into the box1 he can do this      
without bringing about the collapse of  
the arch2 the only essential condition  
is that the bottom shall be keyed up    
tightly1 so as not to allow the escape  
of any sand4 ,he is also referred to the
 two photographs1 ,plate ,,xxiv1        
illustrating the writer's first         
experiment1 showing how increases in the
 loading resulted in compacting the     
material of the arch and in the         
consequent lowering of the false bottom4
 ,as long as the exposed sand above this
 false bottom had cohesion enough to    
prevent the collapse of the centering1  
this arch could have been loaded with   
safety up to the limits of the          
compressive strength of the sand4  ,to  
quote again from ,mr4 ,goodrich3        

,furthermore1 the author's reason for   
bisecting the angle between      the    
vertical and the angle of repose of the 
material1 when he      undertakes to    
determine the thickness of key1 is not  
obvious4 ,this      assumption is shown 
to be absurd when carried to either     
limit1 for      when the angle of repose
 equals zero1 as is the case with water1
      this method would give a definite 
thickness of key1 while there can       
be absolutely no arch action possible in
 such a case2 and1 when the      angle  
of repose is #ij1 as may be assumed in  
the case of rock1 this      method would
 give an infinite thickness of key1     
which is again seen      to be absurd4  
,mr4 ,goodrich assumes that water or    
liquid has an angle of repose equal to  
zero1 which is true1 but the writer's   
assumptions applied only to solid       
material1 and the liquid gives an       
essentially different condition of      
pressure1 as shown by a careful reading 
of the paper4 ,in solid rock ,mr4       

,goodrich assumes an angle of repose    
equal to #ij1 for which there is no     
authority2 that is1 solid rock has no   
known angle of repose4 ,in order to     
carry these assumptions to a definite   
conclusion1 we must assume for that     
material with an angle of repose of #ij 
some solid material which has weight but
 no thrust1 such as blocks of ice piled 
vertically4 ,in this case ,mr4 ,goodrich
 can readily see that there will be no  
arching action over the structure1 and  
that the required thickness of key would
 be infinite4 ,as to the other case1 it 
is somewhat difficult to conceive of a  
solid with an angle of repose of zero2  
aqueous material does not fulfill this  
condition1 as it is either a liquid or a
 combination of water and solid         
material4 ,the best illustration1       
perhaps1 would be to assume a material  
composed of iron filings1 into which had
 been driven a powerful magnet1 so that 
the iron filings would be drawn         
horizontally in one direction4 ,it is   

easy to conceive1 then1 that in         
tunneling through this material there   
would be no necessity for holding up the
 roof2 the definite thickness of key    
given1 as being at the point of         
intersection of two #de angles1 would be
 merely a precautionary measure1 and    
would not be required in practice4  ,it 
is thus seen that both these conditions 
can be fulfilled with practical         
illustrations2 that is1 for an angle of 
repose of #ij1 that material which has  
weight and no thrust1 and for an angle  
of repose of zero1 that solid material  
which has thrust but no weight4  ,mr4   
,goodrich says the author has given no  
experiments to prove his statement that 
the arch thrust is greater in dryer     
sand4 ,if ,mr4 ,goodrich will make the  
experiment partially described as       
,experiment ,no4 #c1 with absolutely dry
 sand1 and with moist sand1 and on a    
scale large enough to eliminate         
cohesion1 he will probably find enough  
to convince him that in this assumption 

the writer is correct4 ,at the same     
time1 the writer has based his theory in
 this regard on facts which are not     
entirely conclusive1 and his mind is    
open as to what future experiments on a 
large scale may develop4 ,it is very    
probable1 however1 that an analytical   
and practical examination of the        
,english experiments noted on pages #cgi
 and #chj1 will be sufficient to develop
 this fact conclusively4  ,the writer is
 forced to conclude that some of the    
criticisms by ,mr4 ,goodrich result from
 a not too careful reading of the paper4
 ,for instance1 he states3       ',it is
 conceded' 7line #b1 p4 #ceg1 for       
example7 when the writer1      for one1 
has not even conceded the accuracy of   
the assumptions4  ,a more careful       
reading would have shown ,mr4 ,goodrich 
that this concession was one of the     
writer's as to certain pressures against
 or on tunnels1 and1 if ,mr4 ,goodrich  
does not concede this1 he is even more  
radical than the writer4  ,and again3   

',nor can anyone 99 99 99 doubt that the
 top timbers are stressed more          
heavily than those at the bottom' is    
emphatically doubted and      earnestly 
denied by the writer4  ,it is           
unfortunate that ,mr4 ,goodrich failed  
to make the complete quotation1 which   
reads3       ,nor can anyone1 looking at
 ,fig4 #e1 doubt1 etc4  ,a glance at    
,fig4 #e will demonstrate that1 under   
conditions there set forth1 the writer  
is probably correct in his assertion as 
relating to that particular instance4   
,further3       ,for instance1 the      
author's well-known theory that the     
pressures      against retaining walls  
are a maximum at the top and decrease to
      zero at the bottom1 is in absolute
 contradiction to the results of        
experiments conducted on a large scale  
by the writer on the new      reinforced
 concrete retaining wall near the ,st4  
,george ,ferry1 on      ,staten ,island4
  ,the writer's well-known theory that  
pressures against retaining walls are a 

maximum at the top and decrease to zero 
at the bottom applies only to pressures 
exerted by absolutely dry and normally  
dry material1 and it seems to him that  
this so-called theory is capable of such
 easy demonstration1 by the simple      
observation of any bracing in a deep    
trench in material of this class1 that  
it ought to be accepted as at least     
safer than the old theory which it      
reverses4 ,as to this well-known theory 
in material subject to water pressure1 a
 careful reading of the paper1 or an    
examination of ,fig4 #ab and its        
accompanying text1 or an examination of 
,table #a1 will convince ,mr4 ,goodrich 
that1 under the writer's analysis1 this 
pressure does not decrease to zero at   
the bottom1 but that in soft materials  
it may be approximately constant all the
 way down1 while1 in exceptionally soft 
material1 conditions may arise where it 
may increase toward the bottom4 ,the    
determination should be made by taking  
the solid material and drying it        

sufficiently so that water does not flow
 or seep from it4 ,when this material is
 then compacted to the condition in     
which it would be in its natural state1 
its angle of repose may be measured1 and
 may be found to be as high as #fj      
degrees4 ,the very fine matter should   
then be separated from the coarser      
material1 and the latter weighed1 to    
determine its proportion4 ,subtracting  
this from the total1 the remainder could
 be credited to aqueous matter4 ,it is  
thus seen that with a material when     
partially dried in which the natural    
angle of repose might be #fj1 and in    
which the percentage of water or aqueous
 matter when submerged might be #fj1    
there would be an increase of pressure  
toward the bottom4  ,the writer does not
 know the exact nature of the           
experiments made at ,st4 ,george's      
,ferry by ,mr4 ,goodrich1 but he        
supposes they were measurements of      
pressures on pistons through holes in   
the sheeting4 ,he desires to state again

 that he cannot regard such experiments 
as conclusive1 and believes that they   
are of comparative value only1 as such  
experiments do not measure in any large 
degree the pressure of the solid        
material but only all or a portion of   
the so-called aqueous matter1 that is1  
the liquid and very fine material which 
flows with it4 ,thus it is well known   
that1 during the construction of the    
recent ,hudson and ,north ,river        
,tunnels1 pressures were tested in the  
silt1 some of which showed that the silt
 exerted full hydrostatic pressure4 ,at 
the same time1 ,w4,i4 ,aims1 ,m4 ,am4   
,soc4 ,c4 ,e41 stated in a public       
lecture1 and recently also to the       
writer1 that in #ahij he made some tests
 of the pressure of this silt in normal 
air for the late ,w4,r4 ,hutton1 ,m4    
,am4 ,soc4 ,c4 ,e4 ,a hole1 #ab in4     
square1 was cut through the brickwork   
and the iron lining1 just back of the   
lock in the north tube 7in normal air71 
and about #ajjj ft4 from the ,new       

,jersey shore4 ,it was found that the   
silt had become so firm that it did not 
flow into the opening4 ,later1 a #d-;in4
 collar and piston were built into the  
opening1 and1 during a period covering  
at least #c months1 constant            
observations showed that no pressure    
came upon it2 in fact1 it was stated    
that the piston was frequently worked   
back and forth to induce pressure1 but  
no response was obtained during all this
 period4 ,the conclusion must then be   
drawn that when construction1 with its  
attendant disturbance1 has stopped1 the 
solid material surrounding structures   
tends to compact itself more or less1   
and solidify1 according as it is more or
 less porous1 forming in many instances 
what may be virtually a compact arch    
shutting off a large percentage of the  
normal1 and some percentage even of the 
aqueous1 pressure4  ,that the pressure  
of normally dry material cannot be      
measured through small openings can be  
verified by any one who will examine    

such material back of bracing showing   
evidences of heavy pressure4 ,the       
investigator will find that1 if this    
material is free from water pressure1   
paper stuffed lightly into small        
openings will hold back indefinitely    
material which in large masses has      
frequently caused bracing to buckle and 
sheeting planks to bend and break2 and  
the writer reiterates that such         
experiments should be made in trenches  
sheeted with horizontal sheeting bearing
 against short vertical rangers and     
braces giving horizontal sections       
absolutely detached and independent of  
each other4 ,in no other way can such   
experiments be of real value 7and even  
then only when made on a large scale7 to
 determine conclusively the pressure of 
earth on trenches4  ,as to the questions
 of the relative thrust of materials    
under various angles of repose1 and of  
the necessity of dividing by the        
tangent1 etc42 these1 to the writer1    
seem to be merely the solution of       

problems in simple graphics4  ,the      
writer believes that if ,mr4 ,goodrich  
will make1 even on a small scale1 some  
of the experiments noted by the writer1 
he will be convinced that many of the   
assumptions which he cannot at present  
endorse are based on fact1 and his      
co-operation will be welcomed with the  
greatest interest4 ,among the           
experiments which he is asked to make is
 the one in dry sand1 noted as          
,experiment ,no4 #c1 whereby it can be  
shown very conclusively that additional 
back-fill will result in increased      
arching stability1 on an arch which     
would collapse under lighter loading4   
,the writer is indebted to ,mr4         
,goodrich for pointing out some errors  
in omission and in typography 7now      
corrected71 and for his hearty          
concurrence in some of the assumptions  
which the writer believed would meet    
with greatest disapproval4  ,in reply to
 ,mr4 ,pruyn and ,mr4 ,gregory1 the     
writer assumed that the piston area in  

,experiment ,no4 #f should be reduced   
only by the actual contact of material  
with it4 ,if this material in contact   
should be composed of theoretical       
spheres1 resulting in a contact with    
points only1 then the theoretical area  
reduced should be in proportion to this 
amount only4 ,the writer does not       
believe1 however1 that this condition   
exists in practice1 but thinks that the 
area is reduced very much more than by  
the actual theoretical contact of the   
material4 ,he sees no reason1 as far as 
he has gone1 to doubt the accuracy of   
the deductions from this experiment4    
,regarding the question of the length of
 time required to raise the piston1 he  
does not believe that the position of   
his critics is entirely correct in this 
matter2 that is1 it must either be      
conceded that the piston area is cut off
 from the source of pressure1 or that it
 is in contact with it through more or  
less minute channels of water4 ,if it is
 cut off1 then the writer's contention  

is proved without the need of the       
experiment1 and it is therefore         
conclusive that a submerged tunnel is   
not under aqueous pressure or the       
buoyant action of water4 ,if1 on the    
other hand1 the water is in contact     
through channels bearing directly upon  
the piston and leading to the clear     
water chamber1 any increase in pressure 
in the water chamber must necessarily   
result in a virtually instantaneous     
increase of the pressure against the    
piston1 and therefore the action on the 
latter should follow almost immediately4
 ,in all cases during the experiments   
the piston did not respond until the    
pressure was approximately twice as     
great as required in clear water1       
therefore the writer must conclude      
either that the experiments proved it   
conclusively or that his assumption is  
proved without the necessity of the     
experiments4 ,that is1 the pressure is  
virtually not in evidence until the     
piston has commenced to move4  ,mr4     

,pruyn has added valuable information in
 his presentation of data obtained from 
specific tests of the bearing value of1 
and friction on1 hollow steel piles4    
,these data largely corroborate tests   
and observations by the writer1 and are 
commended to general attention4  ,mr4   
,carter's information is also of special
 interest to the writer1 as much of it  
is in the line of confirming his views4 
,mr4 ,carter does not yet accept the    
theory of increased pressure toward the 
top1 but if he will examine or          
experiment with heavy bracing in deep   
trenches in clear sand1 or material with
 well-defined angles of repose1 he will 
probably find much to help him toward   
the acceptance of this view4  ,the      
writer regrets that he has not now the  
means or appliances for further         
experiments with the piston chamber1 but
 he does not believe that reliable      
results could be obtained in broken     
stone with so small a piston1 as it is  
possible that the point of one stone    

only might be in contact with the       
piston4 ,this would naturally leave the 
base exposed almost wholly to a clear   
water area4 ,he does not believe1       
however1 that in practice the laying of 
broken stone under inverts will         
materially change the ultimate pressure 
unless its cross-section represents a   
large area4  ,mr4 ,perry will find the  
following on page #cfi3       ,it should
 be noted also that although the area   
subject to pressure      is diminished1 
the pressure on the area remaining      
corresponds to      the full hydrostatic
 head1 as would be shown by the pressure
 on an      air gauge4  ,this1 of       
course1 depends on the porosity of the  
material and the friction the water     
meets in passing through it4  ,as to    
,mr4 ,thomson's discussion1 the writer  
notes with regret two points3 7a7 that  
specific data are not given in many of  
the interesting cases of failures of    
certain structures or bracing2 and 7b71 
that he has not in all cases a clear    

understanding of the paper4 ,for        
instance1 the writer has not advocated  
the omission of bottom bracing or       
sheeting4 ,he has seen many instances   
where it has been1 or could have been1  
safely omitted1 but he desires to make  
it clear that he does not under any     
circumstances advocate its omission in  
good work2 but only that1 in            
well-designed bracing1 its strength may 
be decreased as it approaches the       
bottom4  ,reference is again made to the
 diagram1 ,fig4 #ab1 which shows that1  
in most cases of coffer-dams in combined
 aqueous and earth pressure1 there may  
be nearly equal1 and in some cases even 
greater1 loading toward the bottom4     
,the writer also specifically states    
that in air the difference between      
aqueous and earth pressure is plainly   
noted by the fact that bracing is needed
 so frequently to hold back the earth   
while the air is keeping out the water4 
,the lack of specific data is especially
 noticeable in the account of the rise  

of the #f-;ft4 conduit at ,toronto4 ,it 
would be of great interest to know with 
certainly the weight of the pipe per    
foot1 and whether it was properly bedded
 and properly back-filled4 ,in all      
probability the back-filling over       
certain areas was not properly done1 and
 as the pipe was exposed to an upward   
pressure of nearly #afjj lb4 per ft41   
with probably only #ejj or #fjj lb4 of  
weight to counterbalance it1 it can     
readily be seen that it did not conform 
with the writer's general suggestion1   
that structures not compactly1 or only  
partially1 buried1 should have a large  
factor of safety against the upward     
pressure4 ,opposed to ,mr4 ,thomson's   
experience in this instance is the fact 
that oftentimes the tunnels under the   
,east ,river approached very close to   
the surface1 with the material above    
them so soupy 7owing to the escape of   
compressed air7 that their upper        
surfaces were temporarily in water1 yet 
there was no instance in which they     

rose1 although some of them were under  
excessive buoyant pressure4  ,it is also
 of interest to note1 from the papers   
descriptive of the ,north ,river        
,tunnel1 that1 with shield doors closed1
 the shield tended to rise1 while by    
opening the doors to take in muck the   
shield could be brought down or kept    
down4 ,the writer concurs with those who
 believe that the rising of the shield  
with closed doors was due to the        
slightly greater density of the material
 below1 and was not in any way due to   
buoyancy4  ,concerning the collapse of  
the bracing in the tunnel built under a 
side-hill1 the writer believes it was   
due to the fact that it was under a     
sliding side-hill1 and that1 if it had  
been possible to have back-filled over  
and above this tunnel to a very large   
extent1 this back-fill would have       
resulted in checking the sliding of     
material against the tunnel1 and the    
work would thereafter have been done    
with safety4 ,this is corroborated by   

,mr4 ,thomson's statement that the      
tunnel was subsequently carried through 
safely by going farther into the hill4  
,as to the angle of repose1 ,mr4        
,thomson seems to feel that its         
determination is so often impracticable 
that it is not to be relied on2 and yet 
all calculations pertaining to earth    
pressure must be based on this factor4  
,the writer believes that the angle of  
repose is not difficult to determine1   
and that observations of1 and           
experiments on1 exposed banks in similar
 material1 and general experience in    
relation thereto1 will enable one to    
determine it in nearly all cases within 
such reasonably accurate limits that    
only a small margin of safety need be   
added4  ,engineers are sent to ,europe  
to study sewage disposal1 water         
purification1 transit problems1 etc41   
but are rarely sent to an adjoining     
county or ,state to look at an exposed  
bank1 which would perhaps solve a vexed 
problem in bracing and result in great  

economy in the design of permanent      
structures4  ,mr4 ,thomson's general    
views seem to indicate that much of the 
subject matter noted in the paper       
relates to unsolvable problems1 for it  
appears that in many cases he believes  
the ,engineer to be dependent on his    
educated guess1 backed perhaps by the   
experienced guess of the foreman or     
practical man4 ,the writer1 on the      
contrary1 believes that every problem   
relating to work of this class is       
capable of being solved1 within         
reasonably accurate limits1 and that the
 time is not far distant when the       
engineer1 with his study of conditions1 
and samples of material before him1 will
 be able to solve his earth pressure and
 earth resistance problems as accurately
 as the bridge engineer1 with his       
knowledge of structural materials1      
solves bridge problems4  ,the writer1 in
 the course of his experience1 has met  
with or been interested in the solution 
of many problems similar to the         

following3  ,what difference in         
timbering should be made for a tunnel in
 ordinary1 normally dry ground at a     
depth of #bj ft4 to the roof1 as        
compared with one at a depth of #ij ft48
  ,what difference in timbering or in   
permanent design should be made for a   
horizontally-sheeted shaft1 #e ft4      
square1 going to a depth of #de ft4 and 
one #be by #gj ft41 for instance1 going 
to the same depth1 assuming each to be  
braced and sheeted horizontally with    
independent bracing8  ,what allowance   
should be made for the strength of      
interlock1 assuming that a circular     
bulkhead of sand1 #cj ft4 in diameter1  
is to be carried by steel sheet-piling  
exposed around the outside for a depth  
of #dj ft48  ,what average pressure per 
square foot of area should be required  
to drive a section of a #c by #ae-;ft4  
roof shield1 as compared with the       
pressure needed to drive the whole roof 
shield with an area four times as great8
  ,to what depth could a #ab by #ab-;in4

 timber be driven1 under gradually added
 pressure1 up to #fj tons1 for instance1
 in normal sand8  ,what frictional      
resistance should be assumed on a       
hollow1 steel1 smooth-bore pile which   
had been driven through sharp sand and  
had penetrated soft1 marshy material the
 bearing resistance of which was        
practically valueless8  ,what allowance 
should be made for the buoyancy of a    
tunnel #bj ft4 in diameter1 the top of  
which was buried to a depth of #bj ft4  
in sand above which there was #dj ft4 of
 water8  ,it is believed by the writer  
that most of the authorities are silent 
as to the solution of problems similar  
to the above1 and it is because of this 
lack of available data that he has      
directed his studies to them4 ,the      
belief that the results of these        
studies1 together with such observations
 and experiments as relate thereto1 may 
be of interest1 has caused him to set   
them forth in this paper4  ,he desires  
to state his belief that if problems    

similar to the above were given for     
definite solution1 not based on ordinary
 safe practice1 and without conference1 
to a number of engineers prominently    
interested in such matters1 the results 
would vary so widely as to convince some
 of the critics of this paper that the  
greater danger lies rather in the       
non-exploration of such fields than in  
the setting forth of results of         
exploration which may appear to be      
somewhat radical4  ,further1 if these   
views result in stimulating enough      
interest to lead to the hope that       
eventually the ,pressure1 ,resistance1  
and ,stability of ground under varying  
conditions will be known within         
reasonably accurate limits and          
tabulated1 the writer will feel that his
 efforts have not been in vain4         
,,footnotes3  ,footnote ,h3 ,lateral    
,earth ,pressures and ,related          
,phenomena1 ,transactions1 ,am4 ,soc4   
,c4 ,e41 ,vol4 ,,liii1 p4 #bgb4