,transcriber's ,notes3 ,underscores 80 before and after a word or phrase indicate italics in the original text4 ,small capitals have been converted to ,,solid capitals4 ,illustrations have been moved so they do not break up paragraphs4 ,typographical and punctuation errors have been silently corrected4 ,,earth ,,dams ,a ,,study ,,by ,,burr ,,bassell1 ,m4 ,am4 ,soc4 ,c4 ,e4 ,consulting ,engineer ,,new ,,york ,,the ,,engineering ,,news ,,publishing ,,company #aijd ,,copyright1 #aijd ,,by ,,the ,,engineering ,,news ,,publishing ,,co4 ,,acknowledgments4 ,the writer wishes to acknowledge his appreciation of the assistance given him by ,mr4 ,jas4 ,d4 ,schuyler1 ,m4 ,am4 ,soc4 ,c4 ,e41 ,consulting ,hydraulic ,engineer1 in reviewing this paper1 and in making suggestions of value4 ,appendix ,,ii contains a list of authors whose writings have been freely consulted1 and to whom the writer is indebted2 the numerous citations in the body of the paper further indicate the obligations of the writer4 ,,contents4 ,,page ,,chapter ,i4 ,introductory #a ,,chapter ,,ii4 ,preliminary ,studies and ,investigations #c ,,chapter ,,iii4 ,outline ,study of ,soils4 ,puddle #ab ,,chapter ,,iv4 ,the ,tabeaud ,dam1 ,california #ag ,,chapter ,v4 ,different ,types of ,earth ,dams #cc ,,chapter ,,vi4 ,conclusions #fc ,,appendix ,i4 ,statistical ,descriptions of ,high ,earth ,dams #fg ,,appendix ,,ii4 ,works of ,reference #fh ,,illustrations4 ,,page ,fig4 #a4 ,longitudinal ,section of ,yarrow ,dam ,site #aj #b4 ,cross-,section of the ,yarrow ,dam #aj #c4 ,plan of the ,tabeaud ,reservoir #ag #d4 ,tabeaud ,dam3 ,plan ,showing ,bed ,rock ,drains #ah #e4 ,details of ,drains #ah #f4 ,view of ,drains #ai #g4 ,north ,trench #bj #h4 ,south ,trench #ba #i4 ,main ,central ,drain #ba #aj4 ,embankment ,work #bc #aa4 ,dimension ,section #bf #ab4 ,cross and ,longitudinal ,sections #bg #ac4 ,view of ,dam ,immediately ,after ,completion #bi #ad4 ,cross-,section of ,pilarcitos ,dam #cd #ae4 ,san ,andres ,dam #cd #af4 ,ashti ,tank ,embankment #ce #ag4 ,typical ,new ,england ,dam #dj #ah4 ,two ,croton ,valley ,dams ,showing ,saturation #da #ai4 ,studies of ,board of ,experts on the ,original ,earth ,portion of the ,new ,croton ,dam #dc #bj4 ,studies of ,jerome ,park ,reservoir ,embankment #df #ba to #bd4 ,experimental ,dikes and ,cylinder ,employed in ,studies for the ,north ,dike of the ,wachusett ,reservoir #di #be4 ,cross-,section of ,dike of ,wachusett ,reservoir #di #bf4 ,working ,cross-,section of ,druid ,lake ,dam #ec #bg to #bi4 ,designs for the ,bohio ,dam1 ,panama ,canal #ee #cj4 ,cross-,section of the ,upper ,pecos ,river ,rock-,fill ,dam #ei #ca4 ,developed ,section of the ,san ,leandro ,dam #ei ,,earth ,,dams ,,chapter ,i4 ,introductory4 ,the earth dam is probably the oldest type of dam in existence1 antedating the ,christian ,era many hundreds of years4 ,the literature upon this subject is voluminous1 but much of it is inaccessible and far from satisfactory4 ,no attempt will here be made to collate this literature or to give a history of the construction of earth dams1 however interesting such an account might be4 ,the object will rather be to present such a study as will make clear the application of the principles underlying the proper design and erection of this class of structures4 ,in no way1 therefore1 will it assume the character or dignity of a technical treatise4 ,dams forming storage reservoirs1 which are intended to impound large volumes of water1 must necessarily be built of considerable height1 except in a very few instances where favorable sites may exist4 ,recent discussions would indicate that a new interest has been awakened in the construction of high earth dams4 ,as related to the general subject of storage1 it is with the high structure rather than the low that this study has to do4 ,to the extent that 8the greater includes the less10 the principles here presented are applicable to works of minor importance4 ,many persons who should know better place little importance upon the skill required for the construction of earthwork embankments1 considering the work to involve no scientific problems4 ,it is far too common belief that any ordinary laborer1 who may be able to use skillfully a scraper on a country road1 is fitted to superintend the construction of an earth dam4 ,it has been said that the art of constructing earth dams is purely empirical1 that exact science furnishes no approved method of determining their internal stresses1 and that in regard to their design experience is much more valuable than theory4 ,when the question of stability is fully taken into consideration1 it certainly requires a large amount of skill successfully to carry out works of this character4 ,extreme care in the selection of the site1 sound judgment in the choice of materials and assiduity in superintending the work while in progress1 are all vitally essential4 ,classification of ,dams4 ,dams may be classified according to their purpose as diverting dams or weirs and as storage dams4 ,the former may be located upon any portion of a stream where the conditions are favorable1 and the water used for manifold purposes1 being conveyed by means of canals1 flumes1 tunnels and pipe-lines to places of intended use4 ,these dams are generally low and may be either of a temporary or permanent character1 depending upon the uses to which the water is put4 ,temporary dams are made of brush1 logs1 sand bags1 gravel and loose rock4 ,the more permanent structures are built of stone and concrete masonry4 ,storage dams may be classified according to the kind of material entering into their structure1 as follows3 7#a7 ,earth2 7#b7 ,earth and ,timber2 7#c7 ,earth and ,rock-fill2 7#d7 ,rock-fill2 7#e7 ,masonry2 7#f7 ,composite ,structures4 ,low dams forming service reservoirs for domestic water supplies and for irrigation comprise by far the most numerous class4 ,they are not designed to impound a large volume of water and therefore may be built across a small ravine or depression1 or even upon the summit of a hill1 by excavating the reservoir basin and using the material excavated to form the embankment4 ,these reservoirs may be used in connection with surface or gravity systems1 artesian wells1 or underground supplies obtained by pumping4 ,the dams forming these reservoirs being of moderate size and height may vary greatly in shape and dimensions4 ,the form may be made to suit the configuration of the dam site4 ,when the earthwork requires it1 they may be lined with various materials to secure water-tightness4 ,often such dams are made composite in character1 partly of earth and partly of masonry or some other material4 ,they are also frequently accompanied by numerous accessories1 such as settling-basins1 aerating devices and covers1 which present a diversity in form and appearance4 ,a presentation of the different types of dams thus employed1 with a discussion of the questions pertaining to utility in design and economy in construction1 would be exceedingly valuable and of general interest4 ,service reservoirs will receive only a passing notice1 with the hope expressed that some competent authority will discuss them in the future4 ,,chapter ,,ii4 ,preliminary ,studies and ,investigations4 ,the preliminary studies and investigations which should be made prior to the construction of any dam for the storage of water have to do with 7#a7 the ,catchment ,area1 7#b7 the ,reservoir basin1 and 7#c7 the ,dam site4 ,catchment ,area4 ,it is thought desirable to define a number of terms as we proceed1 for the purpose of correcting erroneous usage and for a clearer understanding of the subject4 ,the catchment area of a reservoir is that portion of the country naturally draining into it4 ,the watershed is the boundary of the catchment area and may be correctly defined as the divide between adjacent drainage systems4 ,in regard to the catchment area it is necessary to determine3 #a4 ,its extent and area in square miles4 #b4 ,its topography or the character of its surface4 #c4 ,its hydrography or precipitation and run-off4 #d4 ,its geology1 or the character of its soils and subsoils1 and the nature and dip of its rock strata4 #e4 ,its flora1 or the extent to which it is clothed with forest trees or other vegetation4 ,all of these elements affect the volumes of maximum run-off1 which is the one important factor in the construction of earth dams that must not be underestimated4 ,if the proposed dam or reservoir is to be located upon a main drainage line2 that is1 upon a river or stream1 it is necessary to know both the flood and low-water discharge of the stream4 ,frequently no reliable data on this subject are available1 and the engineer must then make such a study of the whole situation as will enable him to estimate the minimum and maximum flow with considerable accuracy4 ,there are numerous factors entering into the solution of this first problem1 such as the shape and length of the catchment area1 its general elevation1 the character of its surface1 whether mountainous1 hilly or flat1 barren or timbered4 ,good topographic maps1 if available1 furnish valuable data on these subjects and it is to be regretted that only a comparatively small portion of the ,united ,states has been thus mapped in detail4 ,the results of stream measurements1 if any have been made in the catchment basin1 are especially important3 ,these are usually few in the high areas1 on account of their inaccessibility4 ,the year #aijb marked a notable beginning of such measurements in ,california4 ,in many parts of the arid region of the ,united ,states1 the best storage-sites are situated in the upper or higher portions of the drainage systems4 ,this is especially true of the streams on the ,pacific ,slope having their source in the ,high ,sierras4 ,as regulators of stream-flow and for power purposes such storage is peculiarly valuable1 while storage for irrigation and domestic uses may be located nearer the valleys and the centers of population4 ,frequently the engineer is required to build his dam where no such data are available4 ,in such instances he should endeavor to secure the establishment of rain gauges and make measurements of the flow of the main stream and its principal tributaries at various places to obtain the desired information4 ,even this may not suffice1 owing to the limited time at his disposal1 and he must resort to the use of certain empirical rules or formulas1 and make such comparisons and deductions from known conditions and results as will best answer his purpose4 ,the engineer should know1 approximately at least1 the normal yield of the catchment area1 the duration of the minimum and maximum seasonal flow1 and the floods he may have to provide against during the construction of his dam4 ,these data are absolutely necessary to enable him to provide ample wasteways for his reservoirs4 ,many of the failures of earth dams have been the result of over-topping the embankment1 which would have been averted by an ample wasteway4 ,the most notable example of this kind in recent years was that of the ,south ,fork ,dam1 at ,conemaugh1 ,pennsylvania1 in #ahhi1 resulting in what is generally known as the 8,johnstown ,disaster40 ,there are several empirical rules and formulas for calculating the run off from catchment areas and for determining the size of spillways necessary to discharge this flow with safety to the dam4 ,the proper formula to apply in any given case1 with the varying coefficients of each1 involves a thorough knowledge on the part of the designing engineer of the principles upon which the different factors are based4 ,it is unwise and often hazardous to make use of any important hydraulic formula without knowing the history of its derivation4 ,experiments are not always properly conducted1 and often the deductions therefrom are unreliable4 ,a presentation and discussion of these formulas would require more space than can be given in this study1 and the technical reader must therefore consult for himself1 as occasion may require1 the various authorities cited4 ,formulas for the discharge or run-off from catchment areas1 as determined by ,messrs4 ,craig1 ,dickens1 ,ryves and others1 are given by most writers on the subject of hydraulics4 ,reservoir ,basin4 ,the next subject of inquiry relates to the reservoir basin4 ,it is necessary that its area and capacity at different depths should be definitely known1 and this information can only be obtained by having the basin surveyed and contoured4 ,a map should be made showing contours at intervals of #b to #aj ft41 depending upon the size of the basin and the use to which the reservoir is to be put4 ,reservoir basins have been classified according to their location as follows3 #a4 ,natural lakes4 #b4 ,natural depressions on main drainage lines4 #c4 ,natural depressions on lateral drainage lines4 #d4 ,arbitrary and artificially constructed basins4 ,natural lakes may need to be investigated more or less thoroughly to determine the character of their waters1 whether saline1 alkaline or fresh4 ,it may also be necessary to know their normal depth and capacity1 and to make a study of their outlet if they have one4 ,in some instances the storage capacity of a lake may be enormously increased by means of a comparatively low and inexpensive embankment4 ,the area of reservoir basin1 mean depth1 temperature of the water1 exposure of wind and sunshine1 losses by seepage and evaporation1 all have a bearing upon the available water supply and influence the design of the dam and accessories to the reservoir4 ,in determining the character and suitability of materials for constructing a dam it is necessary to make a careful study of the soil and geological formation4 ,this is best accomplished by digging numerous test pits over the basin1 especially in the vicinity of the proposed dam site2 borings alone should never be relied upon for this information4 ,for such an investigation the advisability of borrowing material for dam construction from the reservoir basin is determined4 ,the porous character of the subsoil strata1 or the dip and nature of the bed rock1 may forbid the removal of material from the floor of the basin1 even at a remote distance from the dam site4 ,the area to be flooded should be cleared and grubbed more or less thoroughly1 depending again upon the use for which the water is impounded4 ,in no instance should timber be left standing below the high-water level of the reservoir2 and all rubbish liable to float and obstruct the outlet tunnel and spillway during a time of flood should be removed4 ,the accessories to a reservoir1 to which reference has been made1 may be enumerated as follows3 #a4 ,outlet pipes or tunnel4 #b4 ,gate tower1 screens and controlling devices4 #c4 ,sluiceways for silt or sand4 #d4 ,wasteway channel or weir4 #e4 ,cover1 settling basin1 aerating devices1 etc4 ,some of these are necessary and common to all classes of reservoirs1 while others are employed only in special cases1 as for domestic water supplies4 ,all reservoirs formed by earth embankments must have at least two of these1 namely a wasteway1 which is its safety valve1 and outlet pipes or outlet tunnel4 ,it may be stated that the proper location and construction of the outlet for a reservoir are of vital importance1 since either to improper location or faulty construction may be traced most of the failures of the past4 ,it is almost impossible to prevent water under high pressure from following along pipes and culverts when placed in an earth dam4 ,the pipes and culverts frequently leak1 and failure ensues4 ,failure may result from one or more of the following causes3 #a4 ,by improper design and placement of the puddle around the pipes4 #b4 ,by resting the pipes upon piers of masonry without continuous longitudinal support4 #c4 ,by reason of subsidence in the cuts of the embankments and at the core walls1 due to the great weight at these points4 #d4 ,leakage due to inherent defects1 frost1 deterioration1 etc4 ,mr4 ,beardsmore1 the eminent ,english engineer who built the ,dale ,dyke embankment at ,sheffield which failed in #ahfd1 and who was afterwards requested to study and report upon the great reservoirs in ,yorkshire and ,lancashire1 said1 after examination and careful study of reservoir embankment construction1 that 8in his opinion there were no conditions requiring that a culvert or pipes should be carried through any portion of the made bank40 ,the writer would go even further and say that the only admissible outlet for a storage reservoir formed by a high earth dam is some form of tunnel through the natural formation at a safe distance from the embankment4 ,dam ,site4 ,the third preliminary study 7that relating to the dam site itself7 will be considered under three heads3 #a4 ,location4 #b4 ,physical features1 materials1 etc4 #c4 ,foundation4 ,,location4-,the location for a dam is generally determined by the use which is to be made of it1 or by the natural advantages for storage which it may possess4 ,if it be for water power it is very frequently located upon the main stream at the point of greatest declivity4 ,if for storage it may be1 as we have seen1 at the head of a river system1 on one of its tributaries1 or in a valley lower down4 ,the type of dam which should be built at any particular locality involves a thorough knowledge1 not alone of the catchment area and reservoir basin1 but also accurate information regarding the geology of the dam site itself4 ,it would be very unwise to decide definitely upon any particular type of dam without first obtaining such information4 ,too frequently has this been done1 causing great trouble and expense1 if not resulting in a total failure of the dam4 ,the conditions favorable for an earth dam are usually unfavorable for a masonry structure1 and vice versa4 ,again1 there may be local conditions requiring some entirely different type4 ,dams situated upon the main drainage lines of large catchment areas are usually built of stone or concrete masonry1 and designed with large sluiceways and spillways for the discharge both of silt and flood waters4 ,it need scarcely be remarked that1 as a rule1 such sites are wholly unsuited to earthwork construction4 ,it is said1 however1 that 8every rule has at least one exception10 and this may be true of those relating to dam sites1 as will appear later under the head of new types4 ,in a general way1 the location of high earth dams is governed by the configuration of the ground forming the storage basin4 ,it may not be possible1 however1 to decide upon the best available site without careful preliminary surveys and examinations of the geological formation4 ,all earth dams must be provided with a wasteway1 ample to discharge the maximum flood tributary to the reservoir4 ,whatever type of wasteway be adopted1 no reliance should ever be put upon the outlet pipes for this purpose4 ,the outlet should only figure as a factor of safety for the wasteway1 insuring1 as it were1 the accuracy of the estimated flood discharge4 ,the safety of the dam demands that ample provision be made for a volume of water in excess of normal flood discharge4 ,this most necessary adjunct of earth dams may be an open channel1 cut through the rim of the reservoir basin1 discharging into a side ravine which enters the main drainage way some distance below the dam4 ,it may be necessary and possible to pierce the rim by means of a tunnel where its length would not prohibit such a design4 ,lastly1 there may be no other alternative than the construction of an overfall spillway1 at one or both ends of the embankment4 ,this last method is the least desirable of any and should be resorted to only when the others are impracticable2 even then1 the volume of water1 local topography1 geology1 and constructive materials at hand must be favorable to such a design4 ,if they are not favorable it may be asked1 8what then80 ,simply do not attempt to build an earth dam at this site4 ,,physical ,,features1 ,,materials1 ,,etc4-,an investigation of the location and the physical features of the dam site should include a careful and scientific examination of the materials in the vicinity1 to determine their suitability for use in construction4 ,an earth embankment cannot be built without earth1 and an earth dam cannot be built with safety without the right kind of earth material4 ,test pits judiciously distributed and situated at different elevations will indicate whether there is a sufficient amount of suitable material within a reasonable distance of the dam4 ,the type of earth dam best suited for any particular locality1 and its estimated cost1 are thus seen to depend upon the data and information obtained by these preliminary studies4 ,economical construction requires the use of improved machinery and modern methods of handling materials1 but far more important even than these are the details of construction4 ,,foundation4-,we may now assume that our preliminary studies relating to the location and physical features of the dam site are satisfactory4 ,we must next investigate the foundation upon which the dam is to be built4 ,this investigation is sometimes wholly neglected or else done in such a way as to be practically useless4 ,to merely drive down iron rods feeling for so-called bed rock1 or to make only a few bore-holes with an earth auger should in no instance be considered sufficient4 ,borings may be found necessary at considerable depths below the surface and in certain classes of material1 but dug pits or shafts should always be resorted to for moderate depths and whenever practicable4 ,only by such means may the true character of the strata underlying the surface1 and the nature and condition of the bed rock1 if it be reached1 become known4 ,if a satisfactory stratum of impermeable material be found it is necessary also to learn both its thickness and extent4 ,it may prove to be only a 8pocket0 of limited volume1 or if found to extend entirely across the depression lengthwise of the dam site it may 8pinch out0 on lines transversely above or below4 ,shafts and borings made in the reservoir basin and below the dam site will determine its extent in this direction1 knowledge of which is very important4 ,fig4 #a1 showing a longitudinal section of the site of the ,yarrow ,dam of the ,liverpool ,water-,works1 ,england1 illustrates the necessity of such investigation4 ,a bore hole at station #b #jj met a large boulder which at first was erroneously thought to be bed rock4 ,the hole at station #c #ej met a stratum of clay which proved to be only a pocket4 ,the relative elevation of the different strata and of the bed rock formation1 referred to one common datum1 should always be determined4 ,these elevations will indicate both the dip and strike of the rock formation and are necessary for estimating the quantities of material to be excavated and removed1 including estimates of cost4 ,they furnish information of value in determining the rate of percolation or filtration through the different classes of material and the amount of probable seepage1 as will appear later4 ,the cost of excavating1 draining and preparing the floor or foundation for a dam is often very great1 amounting to #bj or #cj of the total cost4 ,fig4 #b is a transverse section of the ,yarrow ,dam4 ,this particular dam has been selected as fairly representative of ,english practice and of typical design4 ,it is one of the most widely known earth dams in existence4 ,illustration3 ,,fig4 #a4-,,longitudinal ,,section ,,of ,,yarrow ,,dam ,,site4 ,illustration3 ,,fig4 #b4-;,,cross-,,section ,,of ,,yarrow ,,dam4 ,at the ,yarrow dam site it was necessary to go #ig ft4 below the original surface to obtain a satisfactory formation or one that was impermeable4 ,a central trench was excavated to bed rock1 parallel to the axis of the dam1 and filled with clay puddle to form a water-tight connection with the rock1 and prevent the water in the reservoir from passing through the porous materials under the body of the embankment4 ,this interesting dam will be more fully described later1 when the different types of earth dams are discussed4 ,,chapter ,,iii4 ,outline ,study of ,soils4 ,puddle4 ,the following study of soils is merely suggestive and is here given to emphasize the importance of the subject1 at the risk of being considered a digression4 ,soil formations are made in one of three ways3 #a4 ,by decomposition of exposed rocks4 #b4 ,by transportation or sedimentation of fine and coarse materials worn from rocks4 #c4 ,by transformation into humus of decayed organic matter4 ,the transforming agencies by which soils succeed rocks in geological progression have been classified as follows3 #a4 ,changes of temperature4 #b4 ,water4 #c4 ,air4 #d4 ,organic life4 ,heat and its counter agent frost are the most powerful forces in nature1 their sensible physical effects being the expansion and contraction of matter4 ,water has two modes of action1 physical and chemical4 ,this agent is the great destroyer of the important forces1 cohesion and friction4 ,cohesion is a force uniting particles of matter and resists their separation when the motion attempted is perpendicular to the plane of contact4 ,friction is a force resisting the separation of surfaces when motion is attempted which produces sliding4 ,the hydrostatic pressure and resultant effect upon submerged surfaces need to be kept constantly in mind4 ,when the surface is impermeable the line of pressure is normal to its plane1 but when once saturated there are also horizontal and vertical lines of pressure4 ,since the strength of an earth dam depends upon two factors1 namely1 its weight and frictional resistance to sliding1 the effect of water upon different materials entering into an earth structure should be most carefully considered4 ,this will therefore occupy a large place in these pages4 ,an earth embankment founded upon rock may become saturated by water forced up into it from below through cracks and fissures1 reducing its lower stratum to a state of muddy sludge1 on which the upper part1 however sound in itself1 would slide4 ,the best preliminary step to take in such a case is to intersect the whole site with wide1 dry1 stone drains1 their depths varying according to the nature of the ground or rock4 ,air contains two ingredients ever active in the process of decomposition1 carbonic acid and oxygen4 ,organic ,life accomplishes its decomposing effect both by physical and chemical means4 ,the effect of organic matter upon the mineral ingredients of the soil may be stated as follows3 #a4 ,by their hydroscopic properties they keep the soil moist4 #b4 ,their decomposition yields carbonic acid gas4 #c4 ,the acids produced disintegrate the mineral constituents1 reducing insoluble matter to soluble plant food4 #d4 ,nitric acid results in nitrates1 which are the most valuable form of nutritive nitrogen1 while ammonia and the other salts that are formed are themselves direct food for plants4 ,vegetable ,humus is not the end of decomposition of organic matter1 but an intermediate state of transformation4 ,decay is a process almost identical with combustion1 where the products are the same1 and the end is the formation of water and carbonic acid1 with a residue of mineral ash4 ,the conditions essential to organic decomposition are also those most favorable to combustion or oxidation1 being 7#a7 access of air1 7#b7 presence of moisture1 and 7#c7 application of heat4 ,now the coperation of these chemical and physical forces1 which are ever active1 is called 8weathering40 ,slate rock1 for instance1 weathers to clay1 being impregnated with particles of mica1 quartz1 chlorite and hornblend4 ,shales also weather to clay1 resulting often in a type of earth which is little more than silicate of aluminum with iron oxide and sand4 ,in the vicinity of the ,tabeaud ,dam1 recently built under the personal supervision of the author1 the construction of which will be described later1 there is to be found a species of potash mica1 which in decomposing yields a yellow clay 7being ochre-colored from the presence of iron71 mixed with particles of undecomposed mica4 ,this material is subject to expansion1 and by reason of its lack of grit and its unctuous character it was rejected or used very sparingly4 ,analysis of this material gave1 ,silica1 #ed4a to #ei4e2 potash1 #a4e to #b4c2 soda1 #b4g to #c4g4 ,soil analysis may be either mechanical or chemical4 ,for purposes of earthwork1 we are most interested in the former1 having to deal with the physical properties of matter4 ,chemical analysis1 however1 will often afford information of great value regarding certain materials entering into the construction of earth dams4 ,the most important physical properties are3 7#a7 ,weight and specific gravity4 7#b7 ,coefficient of friction and angle of repose4 7#c7 ,structure and coloring ingredients4 7#d7 ,behavior toward water4 ,there are two distinct methods of mechanical analysis3 7#a7 ,granulating with sieves1 having round holes4 7#b7 ,elutriating with water1 the process being known as silt analysis4 ,it would require a large volume to present the subject of soil analysis in any way commensurate with its importance4 ,experiments bearing upon the subjects of imbibition1 permeability1 capillarity1 absorption and evaporation1 of different earth materials1 are equally interesting and important4#a ,the permeability of soils will be discussed incidentally in connection with certain infiltration experiments to be given later4 ,puddle4 ,puddle without qualification may be defined as clayey and gravelly earth thoroughly wetted and mixed1 having a consistency of stiff mud or mortar4 ,puddle in which the predominating ingredient of the mixture is pure clay1 is called clay puddle4 ,gravel puddle contains a much higher percentage of grit and gravel than the last-named and yet is supposed to have enough clayey material to bind the matrix together and to fill all the voids in the gravel4 ,the term earthen concrete may also be applied to this class of material1 especially when only a small quantity of water is used in the mixture4 ,these different kinds of puddling materials may be found in natural deposits ready for use1 only requiring the addition of the proper amount of water4 ,it is usually necessary1 however1 to mix1 artificially1 or combine the different ingredients in order to obtain the right proportions4 ,some engineers think grinding in a pug-mill absolutely essential to obtain satisfactory results4 ,puddle is handled very much as cement concrete1 which is so well understood that detailed description is hardly necessary4 ,instead of tampers1 sharp cutting implements are usually employed in putting puddle into place4 ,trampling with hoofed animals is frequently resorted to1 both for the purpose of mixing and compacting4 ,as has been stated1 clays come from the decomposition of crystaline rocks4 ,the purest clay known 7kaolin7 is composed of alumina1 silica and water4 ,the smaller the proportion of silica the more water it will absorb and retain4 ,dry clay will absorb nearly one-third of its weight of water1 and clay in a naturally moist condition #a-f to #a-h its weight of water4 ,the eminent ,english engineers1 ,baker and ,latham1 put the percentage of absorption by clayey soils as high as #dj to #fj4 ,pure clays shrink about #e in drying1 while a mixture by weight of #a clay to #b sand will shrink about #c4 ,it follows1 then1 that the larger the percentage of clay there may be in a mixture the greater will be both the expansion and the contraction4 ,clay materials may be very deceptive in some of their physical properties1 being hard to pick under certain conditions1 and yet when exposed to air and water will rapidly disintegrate4 ,beds of clay1 marl and very fine sand are liable to slip when saturated1 becoming semi-fluid in their nature1 and will run like cream4 ,the cohesive and frictional resistances of clays becoming thus very much reduced when charged with water1 a too liberal use of this material is to be deprecated4 ,the ultimate particles forming clays1 viewed under the microscope1 are seen to be flat and scale-like1 while those of sands are more cubical and spherical4 ,this is a mechanical difference which ought to be apparent to even a superficial observer and yet has escaped recognition by many who have vainly attempted a definition of quicksand4 ,mr4 ,strange recommends filling the puddle trench with material having three parts soil and two parts sand4 ,after the first layer next to bed rock foundation1 which he kneads and compacts1 he would put the layers in dry1 then water and work it by treading1 finally covering to avoid its drying out and cracking4 ,prof4 ,philipp ,forchheimer1 of ,gratz1 ,austria1 one of the highest authorities and experimentalists1 affirms that if a sandy soil contains clay to such an extent that the clay fills up the interstices between the grains of sand entirely the compound is practically impervious4 ,mr4 ,herbert ,m4 ,wilson1 ,c4 ,e41 in his 8,manual of ,irrigation ,engineering10 recommends the following as an ideal mixture of materials3 ,cu4 yds4 ,coarse gravel #a4jj ,fine gravel #j4ce ,sand #j4ae ,clay #j4bj -- ,total #a4gj ,this mixture1 when rolled and compacted1 should give #a4be cu4 yds4 in bulk1 thus resulting in #bf compression4 ,mr4 ,clemens ,herschel suggests the following test of 8good binding gravel30 8,mix with water in a pail to the consistency of moist earth2 if on turning the pail upside down the gravel remains in the pail it is fit for use1 otherwise it is to be rejected40 ,for puddling material he would use such a proportion as will render the water invisible4 ,,chapter ,,iv4 ,the ,tabeaud ,dam1 ,california4 ,the ,tabeaud ,dam1 in ,amador ,county1 ,cal41 built under the supervision of the author for the ,standard ,electric ,co41 is an example of the homogeneous earth dam4 ,a somewhat fuller description and discussion will be given of this dam than of any other1 not on account of its greater importance or interest1 but because it exemplifies certain principles of construction upon which it is desired to put special emphasis4 ,this dam was described in ,engineering ,news of ,july #aj1 #aijb1 to which the reader is referred for more complete information than is given here4 ,illustration3 ,,fig4 #c4-,,plan ,,of ,,tabeaud ,,reservoir1 ,,with ,,contours4 ,illustration3 ,,fig4 #d4-,,plan ,,of ,,tabeaud ,,dam1 ,,showing ,,bed ,,rock ,,drainage ,,system4 ,illustration3 ,,fig4 #e4-;,,details ,,of ,,bed ,,rock ,,drains ,,at ,,the ,,tabeaud ,,dam4 ,fig4 #c is a contour map of the ,tabeaud ,reservoir1 showing the relative locations of the dam1 wasteway and outlet tunnel4 ,fig4 #d shows the bed rock drainage system and the letters upon the drawing will assist in following the explanation given in the text4 ,the whole up-stream half of the dam site was stripped to bed rock4 ,as the work of excavation advanced pockets of loose alluvial soil were encountered1 which were suggestive of a refill1 possibly the result of placer mining operations during the early mining days of ,california4 ,in addition to this were found thin strata of sand and gravel deposited in an unconformable manner4 ,the slate bed rock near the up-stream toe of the dam was badly fissured and yielded considerable water4 ,a quartz vein from #a to #b ft4 in thickness crossed the dam site about #aej ft4 above the axis of the dam4 ,the slate rock above this vein or fault line was quite variable in hardness and dipped at an angle of #dj degrees toward the reservoir4 ,illustration3 ,,fig4 #f4-,,view ,,of ,,bed ,,rock ,,trenches1 ,,tabeaud ,,dam4 ,the rear drain terminates at a weir box 7,z7 outside of the down-stream slope at a distance of #ejj ft4 from the axis of the dam4 ,this drain branches at the down-stream side of the central trench1 7,y71 one branch being carried up the hillside to high-water level 7,w7 at the ,north end of the dam1 and the other to the same elevation at the ,south end 7,x74 ,fig4 #e shows how these drains were constructed4 ,after the removal of all surface soil and loose rock1 a trench #e to #aj ft4 wide was cut into the solid rock1 the depth of cutting varying with the character of the bed rock4 ,upon the floor of this trench a small open drain was made by notching the bed rock and by means of selected stones of suitable size and hardness4 ,the stringers and cap-stones were carefully selected and laid1 so that no undue settlement or displacement might occur by reason of the superincumbent weight of the dam4 ,all crevices were carefully filled with spawls and the whole overlaid #ah ins4 in depth with broken stone #a to #c ins4 in diameter4 ,upon this layer of broken stone and fine gravel was deposited choice clay puddle1 thoroughly wetted and compacted1 refilling the trenches4 ,illustration3 ,,fig4 #g4-,,view ,,of ,,north ,,trench1 ,,tabeaud ,,dam4 ,illustration3 ,,fig4 #h4-,,view ,,of ,,south ,,trench1 ,,tabeaud ,,dam4 ,illustration3 ,,fig4 #i4-,,view ,,of ,,main ,,central ,,drain1 ,,tabeaud ,,dam4 ,these drains served a useful purpose during construction1 in drying off the surface of the dam after rains4 ,the saturation of the outer slope of the dam by water creeping along the line of contact should thus be prevented1 and the integrity or freedom from saturation of the down-stream half should be preserved4 ,it is believed that the puddle overlying these rock drains will effectually prevent any water from entering the body of the embankment by upward pressure and that the drains will thus forever act as efficient safeguards4 ,the main drain was extended1 temporarily during construction1 from the central trench 7,fig4 #d71 to the up-stream toe of the dam4 ,this was cut #e or #f ft4 deep into solid rock1 below the general level of the stripped surface4 ,fig4 #f is reproduced from a photograph of this trench4 ,an iron pipe #b ins4 in diameter was imbedded in ,portland cement mortar and concrete1 and laid near the bottom of the trench4 ,at the point 7,b7 where the quartz vein 7already described7 intersected this drain1 two branch drains were made1 following the fault well into the hill on both sides4 ,figs4 #g and #h are views of the ,north and ,south trenches1 respectively4 ,these trenches were necessary to take care of the springs issuing along the quartz vein4 ,this water led to a point 7,n1 ,fig4 #d7 near the up-stream toe1 by means of the drain shown in ,fig4 #i4 ,the lateral drains and that portion of the main central drain extending from their junction 7,b7 to a point 7,n7 about #bcj ft4 from the axis of the dam have pieces of angle iron or wooden ,y-fluming laid on the bottom of the trenches immediately over the #b-;in4 pipe1 as shown in ,figs4 #g1 #h and #i4 ,these are covered in turn with ,portland cement mortar1 concrete1 clay puddle and earth fill4 ,the water will naturally flow along the line of least resistance1 and consequently will follow along the open space between the angle irons and the outside of the pipe until it reaches the chamber and opening in the pipe1 permitting the water to enter and be conveyed through the imbedded pipe-line to the rear drain4 ,this point of entry is a small chamber in a solid cross-wall of rich cement mortar1 and is the only point where water can enter this pipe-line1 the two branches entering the wells and the stand-pipe at their junction 7soon to be described7 having been closed4 ,that portion of the foundation between the axis of the dam and the quartz vein1 a distance of about #afj ft41 was very satisfactory1 without fissures or springs of water4 ,in this portion the #b-;in4 pipe was imbedded in mortar and concrete without angle irons1 and the continuity of the trench broken by numerous cross-trenches cut into the rock and filled with concrete and puddle4 ,it is believed that no seepage water will ever pass through this portion of the dam4 ,if any should ever find its way under the puddle and through the bed rock formation1 the rear drain1 with its hillside branches1 will carry it away and prevent the saturation of the lower or down-stream half of the dam4 ,illustration3 ,,fig4 #aj4-,,view ,,of ,,tabeaud ,,dam ,,when ,,about ,,half ,,completed4 ,at the up-stream toe of the embankment1 two wells or sumps 7shown at 8,s0 and 8,k10 ,fig4 #d7 were cut #aj or #ab ft4 deeper than the main trench1 which received the water entering the inner toe puddle trench during construction4 ,this water was disposed of partly by pumping and partly by means of the #b-;in4 branch pipes leading into and from these wells4 ,at their junction 7,j7 a #b-;in4 stand-pipe was erected1 which was carried vertically up through the embankment1 and finally filled with cement4 ,the branch pipes from the wells were finally capped and the wells filled with broken stone1 as previously mentioned4 ,,embankment4-,as has been said1 the upper surface of the slate bed rock was found to be badly fissured1 especially near the up-stream toe of the dam1 and as the average depth below the surface of the ground was not very great1 it was thought best to lay bare the bed rock over the entire upper half of the dam site4 ,had the depth been much greater1 it would have been more economical and possibly sufficient to have put reliance in a puddle trench1 alone1 for securing a water-tight connection between the foundation and the body of the dam4 ,at the axis of the dam and near the inner toe1 where the puddle walls abutted against the hillsides1 the excavation always extended to bed rock4 ,vertical steps and offsets were avoided and the cuts were made large enough for horses to turn in while tramping1 these animals being used1 singly and in groups1 to mix and compact the puddle and thus lessen the labor of tamping by hand4 ,in plan1 the hillside contact of natural and artificial surfaces presents a series of corrugated lines1 7as is clearly shown in ,fig4 #d47 ,after all loose and porous materials had been removed1 the stripped surface and the slopes of all excavations were thoroughly wetted from time to time by means of hose and nozzle1 the water being delivered under pressure4 ,fig4 #aj is a view of the dam taken when it was about half finished and shows the work in progress4 ,the face puddle shown in ,fig4 #aa was used merely to 8make assurance doubly sure0 and was not carried entirely up to the top of the dam4 ,the earth of which the dam was constructed may be described as a red gravelly clay1 and in the judgment of the author is almost ideal material for the purpose4 ,physical tests and experiments made with the materials at different times during construction gave the following average results3 ,pounds4 ,weight of #a cu4 ft4 earth1 dust dry #hd4j 8 8 #a 8 saturated earth #aja4h 8 8 #a 8 moist loose earth #gf4f 8 8 #a 8 loose material taken from test pits on the dam #hj4j 8 8 #a 8 earth in place taken from the borrow pits #aaf4e 8 8 #a 8 earth material taken from test pits on the dam #acc4j ,per cent4 ,percentage of moisture in natural earth #ai 8 8 voids in natural earth #eb 8 8 grit and gravel in natural earth #ch 8 8 compression on dam over earth at borrow pit #af 8 8 compression on dam over earth in wagons #dc ,degrees4 ,angle of repose of natural moist earth #dd ,angle of repose of earth1 dust dry #cf ,angle of repose of saturated earth #bc ,,construction ,,details4-,the materials forming the bulk of the dam were hauled by four-horse teams1 in dump wagons1 holding #c cu4 yds4 each4 ,the wagons loaded weighed about six tons and were provided with two swinging bottom-doors1 which the driver could operate with a lever1 enabling the load to be quickly dropped while the team was in motion4 ,if the material was quite dry1 the load could be dumped in a long row when so desired4 ,after plowing the surface of the ground and wasting any objectionable surface soil1 the material was brought to common earth-traps for loading into wagons1 by buck or dragscrapers of the ,fresno pattern4 ,in good material one trap with eight ,fresno-scraper teams could fill #be wagons per hour4 ,the average length of haul for the entire work was about #a1cbj ft4 ,the original plans and specifications were adhered to throughout1 with the single exception that the central puddle wall was not carried above elevation #a1afj1 as shown on ,figs4 #aa and #ab1 more attention being given to the inner face puddle4 ,this modification in the original plans was made because of the character of the materials available and the excellent results obtained in securing an homogeneous earthen concrete1 practically impervious4 ,illustration3 ,,fig4 #aa4-;,,dimension ,,section ,,of ,,tabeaud ,,dam4 ,the top of the embankment was maintained basin-shaped during construction1 being lower at the axis than at the outer slopes by #a-aj1 to the height below the finished crown4 ,this gave a grade of about #a in #be from the edges toward the center1 resulting in the following advantages3 7#a7 ,insuring a more thorough wetting of the central portion of the dam2 any excess of water in this part would be readily taken care of by the central cross drains4 7#b7 ,in wetting the finished surface prior to depositing a new layer of material1 water from the sprinkling wagons would naturally drain towards the center and insure keeping the surface wet2 the layers being carried1 as a rule1 progressively outward from the center4 7#c7 ,it centralized the maximum earth pressure and enabled the depositing of material in layers perpendicular to the slopes4 7#d7 ,it facilitated rolling and hauling on lines parallel to the axis of the dam1 and discouraged transverse and miscellaneous operations4 7#e7 ,it finally insured better compacting by the tramping of teams in their exertions to overcome the grade4 ,illustration ,illustration3 ,,fig4 #ab4-;,,cross ,,and ,,longitudinal ,,sections ,,of ,,tabeaud ,,dam4 ,the specifications stipulated that the body of the dam should be built up in layers not exceeding #f ins4 in thickness for the first #fj ft41 and not exceeding #h ins4 above that elevation4 ,the finished layers after rolling varied slightly in thickness1 the daily average per month being as follows3 ,april #d ins4 ,may #c 8 ,june #d 8 ,july #d 8 ,august #e 8 ,september #f 8 ,october #g 8 ,november and ,december #h 8 ,during the last few months more than one whole layer constituted the day's work1 so that a single layer was seldom as thick as the daily average indicates4 ,it was stipulated in the specifications that the up-stream half of the dam was to be made of 8selected material0 and the lower half of less choice material1 not designated 8waste40 8,waste material0 was described as meaning all vegetable humus1 light soil1 roots1 and rock exceeding #e lbs4 in weight1 too large to pass through a #d-;in4 ring4 ,it may be well to define the expression 8selected material10 so commonly used in specifications for earth dams4 ,in ,england1 for instance1 it is said to refer to materials which insure water-tightness1 while in ,india it refers to those employed to obtain stability4 ,it ought to mean the best material available1 selected by the engineer to suit the requirements of the situation4 ,the method employed in building the body of the embankment may be described as follows3 7#a7 ,the top surface of every finished layer of material was sprinkled and harrowed prior to putting on a new layer4 ,the sprinkling wagons passed over the older finished surface immediately before each wagon-row was begun4 ,this insured a wetted surface and assisted the wheels of the loaded wagons1 as well as the harrows1 to roughen1 the old surface prior to depositing a new layer4 7#b7 ,the material was generally deposited in rows parallel to the axis of the dam4 ,however1 along the line of contact1 at the margins of the embankment1 the earth was often deposited in rows crosswise of the dam1 permitting a selection of the choicest materials and greatly facilitating the work of graders and rollers4 7#c7 ,rock pickers with their carts were continually passing along the rows gathering up all roots1 rocks and other waste materials4 ,illustration3 ,,fig4 #ac4-,,view ,,of ,,tabeaud ,,dam ,,immediately ,,after ,,completion4 7#d7 ,the road-graders drawn by six horses leveled down the tops of the wagon-loads1 and if the material was dry the sprinkling wagons immediately passed over the rows prior to further grading4 ,when the material was naturally moist the grader continued the leveling process until the earth was evenly spread4 ,the depth or thickness of the layer could be regulated to a nicety by properly spacing the rows and the individual loads4 ,the grader brought the layer to a smooth surface and of uniform thickness1 and nothing more could be desired for this operation4 7#e7 ,after the graders had finished1 the harrows passed over the new layer to insure the picking out of all roots and rocks1 followed immediately by the sprinkling wagons4 7#f7 ,finally the rollers thoroughly compacted the layer of earth1 generally passing to and fro over it lengthwise of the dam4 ,along the line of contact at the ends1 however1 they passed crosswise4 ,then again they frequently went around a portion of the surface until the whole was hard and solid4 ,two rollers were in use constantly1 each drawn by six horses4 ,one weighed five tons and the other eight tons1 giving respectively #aff and #bjj lbs4 pressure per lin4 in4 ,they were not grooved1 but the smooth surface left by the rollers was always harrowed and cut up more or less by the loaded wagons passing over the surface previously wetted4 ,the wagons when loaded gave #gej lbs4 pressure per lin4 in41 and the heavy teams traveling wherever they could do the most effective work compacted the materials better even than the rollers4 ,several test pits which were dug into the dam during construction showed that there were no distinct lines traceable between the layers and no loose or dry spots1 but that the whole mass was solid and homogeneous4 ,a careful record is being kept of the amount of settlement of the ,tabeaud ,dam4 ,it will be of interest to record here the fact that just one year after date of completion the settlement amounted to #j4b ft41 with #ij ft4 depth of water in the reservoir4 ,water was first turned into the reservoir five months after the dam was finished4 ,the very small amount of settlement here shown emphasizes more eloquently than words the author's concluding remarks relating to the importance of thorough consolidation1 by artificial means1 of the embankment4 7,see p4 #fd1 ,secs4 #f to #h47 ,,outlet ,,tunnel4-,the outlet for the reservoir is a tunnel #b1ijc ft4 in length1 through a ridge of solid slate rock formation1 which was very hard and refractory4 ,at the north or reservoir end of the tunnel1 there is an open cut #cej ft4 long1 with a maximum depth of #bf ft4 ,near the south portal of the tunnel and in the line of pressure pipes connecting the 8petty reservoir0 above with the power-house below1 is placed a receiver1 connected with the tunnel by means of a short pipe-line1 #fj ins4 in diameter4 ,a water-tight bulkhead of brick and concrete masonry is placed in the tunnel1 at a point about #age ft4 distant from the receiver4 ,in the line of #fj-;in4 riveted steel pipe1 which connects the reservoir and tunnel with the receiver1 there is placed a cast iron chamber for entrapping silt or sand1 with a branch pipe #af ins4 in diameter leading into a side ravine through which sand or silt thus collected can be wasted or washed out4 ,by the design of construction thus described1 it will be seen that all controlling devices1 screens1 gates1 etc41 are at the south end of the tunnel and easily accessible4 ,,wasteway4-,the wasteway for the reservoir is an open cut through its rim1 #dh ft4 in width and #cjj ft4 long4 ,the sill of the spillway is #aj ft4 below the crown of the dam4 ,the reservoir having less than two square miles of catchment area1 and the feeding canals being under complete control1 the dam can never be over-topped by a flood4 ,fig4 #c shows the relative location of the dam1 outlet tunnel and wasteway channel4 ,almost the whole of the embankment forming the ,tabeaud ,dam1 not included in the foundation work1 was built in less than eight months4 ,the contractor's outfit was the best for the purpose the writer has ever seen4 ,after increasing his force from time to time he finally had the following equipment3 #a steam shovel 7#a yds4 capacity71 #cg patent dump wagons1 #aa stick-wagons and rock-carts1 #ci buck-scrapers 7,fresno pattern71 #ba wheel scrapers1 #c road-graders1 #c sprinkling wagons1 #b harrows1 #b rollers 7#e and #h-ton71 #bcc men1 #daf horses and mules1 #h road and hillside plows4 ,,statistics4-,the following data relating to the ,tabeaud ,dam ,reservoir will conclude this description3 ,,dam4 ,length at crown #fcf ft4 ,length at base crossing ravine #ej to #ajj 8 ,height to top of crown 7,el4 #a1beh47 #abj 8 8 at ends above bedrock #aag 8 8 at up-stream toe #ajj 8 8 at down-stream toe #abc 8 ,effective head #aae 8 ,width at crown #bj 8 ,width at base #fbj 8 ,slopes1 #b on #a with rock-fill #c to #a4 ,excavation for foundations #dj1jjj cu4 yds4 ,refill by company #dj1jjj 8 ,embankment built by contractor #ccj1cej 8 ,total volume of dam #cgj1cej 8 ,total weight #ffd1ggh tons4 ,length of wasteway 7width7 #dh ft4 ,depth of spillway sill below crown #aj 8 ,depth of spillway sill below ends #g 8 ,height of stop-planks in wasteway #b 8 ,maximum depth of water in reservoir #ib 8 ,area to be faced with stone #a1icc sq4 yds4 ,,reservoir4 ,catchment area 7approximate7 #b sq4 miles4 ,area of water surface #cf4ge acres4 ,silt storage capacity below outlet tunnel #a1jia1dgj cu4 ft4 ,available water storage capacity #df1fab1dje 8 ,elevation of outlet tunnel #a1ahj ft4 8 8 high-water surface #a1bej 8 8 8 crown of dam #a1beh 8 ,fig4 #ac is a view of the finished dam1 taken immediately after completion4 ,,chapter ,v4 ,different ,types of ,earth ,dams4 ,there are several types of earth dams1 which may be described as follows3 #a4 ,homogeneous earth dams1 either with or without a puddle trench4 #b4 ,earth dams with a puddle core or puddle face4 #c4 ,earth dams with a core wall of brick1 rubble or concrete masonry4 #d4 ,new types1 composite structures4 #e4 ,rock-fill dams with earth inner slope4 #f4 ,hydraulic-fill dams of earth and gravel4 ,the writer proposes to give an example of each type1 with such remarks upon their distinctive features and relative merits as he thinks may be instructive4 ,earth ,dams with ,puddle ,core ,wall or ,face4 ,,yarrow ,,dam4-,the ,yarrow dam of the ,liverpool ,water-,works is a notable example of the second type1 7a section of which is shown in ,fig4 #b47 ,an excavation #ig ft4 in depth was made to bed rock through different strata of varying thickness1 and a trench #bd ft4 wide was cut with side slopes #a on #a for the first #aj ft4 in depth below the surface4 ,the trench was then carried down through sand1 gravel and boulders with sides sloping #a in #ab4 ,the upper surface of the shale bed rock was found to be soft1 seamy and water-bearing4 ,pumps were installed to keep the water out of the trench while it was being cut #d or #e ft4 deeper into the shale4 ,the lower portion was then walled up on either side with brickwork #ad ins4 in thickness1 and the trench between the walls was filled with concrete1 made in the proportion of #a of cement1 #a of sand and #b of gravel or broken stone4 ,by so doing a dry bed was secured for the foundation of the puddle wall4 ,two lines of #f-;in4 pipes were laid on the bed rock1 outside of the walls1 and pipes #i ins4 in diameter extended vertically above the top of the brickwork some #bg ft4 ,these pipes were filled with concrete1 after disconnecting the pumps4 ,after refilling the trench with puddle to the original surface1 a puddle wall was carried up simultaneous with the embankment1 having a decreasing batter of #a in #ab1 which gave a width of #f ft4 at the top4 ,this form of construction is very common in ,england and ,figs4 #ad and #ae show two ,california dams1 the ,pilarcitos and ,san ,andres1 of the same general type4 ,illustration3 ,,fig4 #ad4-;,,cross-,,section ,,of ,,pilarcitos ,,dam4 ,illustration3 ,,fig4 #ae4-;,,cross-,,section ,,of ,,san ,,andres ,,dam4 ,,ashti ,,embankment4-,this is not a very high embankment1 but being typical of modern dams in ,british ,india1 where the puddle is generally carried only to the top of the original surface of the ground1 and not up through the body of the dam1 it is thought worthy of mention4 ,fig4 #af shows a section of this embankment1 which is located in the ,sholapur ,district1 ,india4 ,the central portion of this dam above the puddle trench is made of 8selected black soil20 then on either side is placed 8,brown ,soil10 finishing on the outer slopes with 8,murum40 ,trap rock decomposes first into a friable stony material1 known in ,india as 8,murum0 or 8,murham40 ,this material further decomposes into various argillaceous earths1 the most common being the 8black cotton soil0 mentioned above4 ,illustration3 ,,fig4 #af4-;,,cross-,,section ,,of ,,ashti ,,tank ,,embankment4 ,this particular dam has been adversely criticised on account of the lack of uniformity in the character of the materials composing the bank4 ,it is claimed that the materials being of different density and weight1 unequal settlement will result1 and lines of separation will form between the different kinds of materials4 ,earth materials do not unite or combine with timber or masonry1 but there are no such distinct lines of transition and separation between different earth materials themselves as ,fig4 #af would seem to indicate4 ,puddle ,trench4 ,in the last three dams mentioned 7,figs4 #ad1 #ae1 #af7 the puddle trenches are made with vertical sides or vertical steps and offsets4 ,a wedge-shaped trench certainly has many advantages over this form4 ,puddle being plastic1 consolidates as the dam settles1 filling the lowest parts by sliding on its bed4 ,it thus has a tendency to break away from the portion supported by the step1 and a further tendency to leave the vertical side1 thus forming cracks and fissures for water to enter4 ,the argument advanced by those holding a different view1 namely1 that it is difficult to dress the sides of a trench to a steep batter and to timber it substantially1 has in reality little weight when put to practical test4 ,mr4 ,f4 ,p4 ,stearns1 in describing the recent work of excavating the cut-off trench of the ,north ,dike of the ,wachusett reservoir1 ,boston1 said it was found to be both better and cheaper to excavate a trench with slopes than with vertical sides protected by sheeting4 ,he favored this shape in case of pile-work and for the purpose also of wedging materials together4 ,mr4 ,wm4 ,j4 ,mc,alpine's 8,specifications for ,earth ,dams10 representing the best practice of #be years ago1 which are frequently cited1 contain the following description of how to prepare the up-stream floor of the dam3 ,remove the pervious and decaying matter by breaking up the natural soil and by stepping up the sides of the ravine2 also by several toothed trenches across the bottom and up the sides4 ,one of ,mr4 ,mc,alpine's well known axioms was1 8water abhors an angle40 ,the 8stepping0 and 8toothed0 trenches above specified need not necessarily be made with vertical planes1 but should be made by means of inclined and horizontal planes4 ,the writer's experience and observation leads him to think that all excavations in connection with earth dams requiring a refill should be made wedge-shaped so that the pressure of the superincumbent materials in settling will wedge the material tighter and tighter together and fill every cavity4 ,a paper by ,mr4 ,wm4 ,l4 ,strange1 ,c4 ,e41 on 8,reservoirs with high ,earthen ,dams in ,western ,india10 published in the ,proceedings of the ,institution of ,civil ,engineers1 ,vol4 #acb1 7#ahih71 is one of the best contributions to the literature on this subject1 known to the writer4 ,mr4 ,strange states that the rate of filtration of a soil depends upon its porosity1 which governs the frictional resistance to flow1 and the slope and length of the filamentary channels along which the water may be considered to pass4 ,it is evident1 therefore1 that the direct rate of infiltration in a homogeneous soil must decrease from the top to the bottom of the puddle trench4 ,the best section for a puddle trench is thus a wedge1 such as an open excavation would give4 ,it is true that the uppermost infiltrating filaments when stopped by the puddle1 will endeavor to get under it1 but a depth will eventually be reached when the frictional resistance along the natural passages will be greater than that due to the transverse passage of the puddle trench1 and it is when this occurs that the latter may be stopped without danger1 as the filtration to it will be less than that through it4 ,this depth requires to be determined in each case1 but in fairly compact ,indian soils #cj feet will be a fair limit4 ,puddle ,wall vs4 ,puddle ,trench4 ,there is a diversity of opinion among engineers in regard to the proper place for the puddle in dam construction4 ,theoretically1 the inner face would be preferable to the center1 for the purpose of preventing any water from penetrating the embankment4 ,it is well known that all materials immersed in water lose weight in proportion to the volume of water they displace4 ,if the upper half of the dam becomes saturated it must neccesarily lose both weight and stability4 ,its full cohesive strength can only be maintained by making it impervious in some way4 ,the strength of an earth dam depends upon three factors3 #a4 ,weight4 #b4 ,frictional resistance against sliding4 #c4 ,cohesiveness of its materials4 ,these can be known only so long as no water penetrates the body of the dam4 ,when once saturated the resultant line of pressure is no longer normal to the inner slope1 for the reason that there is now a force tending to slide the dam horizontally and another due to the hydrostatic head tending to lift it vertically4 ,when the water slope is impervious the horizontal thrust is sustained by the whole dam and not by the lower half alone4 ,when once a passage is made into the body of the dam1 the infiltration water will escape along the line of least resistance1 and if there be a fissure it may become a cavity and the cavity a breach4 ,for practical reasons1 mainly on account of the difficulty of maintaining a puddle face on the inner slope of a dam1 which would require a very flat slope1 puddle is generally placed at the center as a core wall4 ,it was thought possible at the ,tabeaud dam to counteract the tendency of the face puddle to slough off into the reservoir by use of a broken stone facing of riprap4 ,this covering will protect the puddle from the deteriorating effects of air and sun whenever the water is drawn low and also resists the pressure at the inner toe of the dam4 ,percolation and ,infiltration4 ,the earlier authorities on the subject of percolation and infiltration of water are somewhat conflicting in their statements1 if not confused in their ideas4 ,we are again impressed with the importance of a clearly defined and definite use of terms4 ,the temptation and tendency to use language synonymously is very great1 but it is unscientific and must result in confusion of thought4 ,let it be observed that filtration is the process of mechanically separating and removing the undissolved particles floating in a liquid4 ,that infiltration is the process by which water 7or other liquid7 enters the interstices of porous material4 ,that percolation is the action of a liquid passing through small interstices2 and1 finally1 that seepage is the amount of fluid which has percolated through porous materials4 ,many recent authorities are guilty of confusion in thought or expression1 as will appear from the following3 ,one says1 for instance1 that a rock is water-tight when non-absorbent of water1 but that a soil is not water-tight unless it will absorb an enormous quantity of water4 ,this would seem to indicate that super-saturation and not pressure is necessary to increase the water-tightness of earth materials4 ,again1 in a recent discussion regarding the saturation and percolation of water through the lower half of a reservoir embankment1 it was remarked1 that the more compact the material of which the bank is built1 the steeper will be the slope of saturation4 ,exception was taken to this1 and the statement made1 that with compact material1 the sectional area of flow is larger below a given level with porous material1 and as the bank slope is one determining factor of the line of saturation1 this line tends to approach the slope line2 while with porous material in a down-stream bank1 the slope of saturation is steeper and the area of the flow less4 ,in reply to this1 it was said1 that it is obvious that if the embankment below the core wall is built of material so compact as to be impervious to water1 no water passing through the wall will enter it1 and the slope of saturation will be vertical4 ,if it be less compact1 water will enter more or less according to the head or pressure1 and according to its compactness or porosity1 producing a slope of saturation whose inclination is dependent on the frictional resistance encountered by the water4 ,and the bank will be tight whenever the slope of saturation remains within the figure of the embankment4 ,further1 that it was necessary to distinguish between the slope assumed by water retained in an embankment and that taken by water passing through an embankment made of material too porous to retain it2 where the rule is clearly reversed and where the more porous the material the steeper the slope at which water will run through it at a given rate4 ,these citations are sufficient to emphasize the importance of exact definition of terms and clear statement of principles4 ,the latest experiments relating to the percolation of water through earth materials and tests determining the stability of soils are those made during the investigations at the ,new ,croton ,dam and ,jerome ,park ,reservoir1 ,new ,york1 and those relating to the ,north ,dike of the ,wachusett ,reservoir1 ,boston4 ,these are very interesting and instructive1 and it is here proposed to discuss the results and conclusions reached in these cases1 after some introductory remarks reciting the order of events4 ,,new ,,croton ,,dam4-,in ,june1 #aija1 the ,board of ,croton ,aqueduct ,commissioners of ,new ,york requested a board of expert engineers1 consisting of ,messrs4 ,j4 ,j4 ,r4 ,croes1 ,e4 ,f4 ,smith and ,e4 ,sweet1 to examine the plans for the construction of the earth portion of the ,new ,croton ,dam1 and also the core wall and embankment of the ,jerome ,park reservoir4 ,this report was published in full in ,engineering ,news for ,nov4 #bh1 #aija4 ,it was followed in subsequent issues of the said journal by supplemental and individual reports from each member of the board of experts1 and by articles from ,messrs4 ,a4 ,fteley1 who originally designed the works1 ,a4 ,craven1 formerly division engineer on this work1 and ,w4 ,r4 ,hill1 at that time chief engineer of the ,croton ,aqueduct ,commission4 ,after describing the ,new ,croton ,dam1 the board of experts preface their remarks on the earth embankment by saying that it has been abundantly proven that up to a height of #fj or #gj ft4 an embankment founded on solid material and constructed of well-selected earth1 properly put in place1 is fully as durable and safe as a masonry wall and far less costly4 ,there are1 in fact1 no less than #bb earth dams in use to-day exceeding #ij ft4 in height1 and twice that number over #gj ft4 in height4 ,five of the former are in ,california1 and several of these have been in use over #be years4 ,the writer fails to appreciate the reason for limiting the safe height of earth dams to #fj or #gj ft4 ,the ,new ,croton ,dam was designed as a composite structure of masonry and earth1 crossing the ,croton ,valley at a point three miles from the ,hudson ,river4 ,the earth portion was to join the masonry portion at a point where the latter was #aie ft4 high from the bed rock4 ,the ,board thought there was no precedent for such a design and no necessity for this form of construction4 ,the point to be considered here was whether a dam like this can be made sufficiently impermeable to water to prevent the outer slope from becoming saturated and thus liable to slide and be washed out4 ,the design of the embankment portion was similar to all the earth dams of the ,croton ,valley4 ,in the center is built a wall of rubble masonry1 generally founded upon solid rock1 and 8intended to prevent the free seepage of water1 but not heavy enough to act alone as a retaining wall for either water or earth40 ,fig4 #ag shows a section which is typical of most ,new ,england earth dams2 and ,fig4 #ah1 the sections of two of the ,croton ,valley dams1 ,new ,york water supply4 ,these dams all have masonry core walls1 illustrating the third type of dams given on page #cc4 ,illustration3 ,,fig4 #ag4-;,,cross-,,section ,,of ,a ,,typical ,,new ,,england ,,dam4 ,the board of experts made numerous tests by means of borings into the ,croton ,valley dams to determine the slope of saturation4 ,the hydraulic laboratory of ,cornell ,university also made tests of the permeability of several samples of materials taken from pits4 ,all the materials examined were found to be permeable and when exposed to water to disintegrate and assume a flat slope1 the surface of which was described as 8slimy40 ,pipe wells were driven at different places into the dams and the line of saturation was determined by noting the elevations at which the water stood in them4 ,in all the dams the entire bank on the water side of the core wall appeared to be completely saturated4 ,water was also found to be standing in the embankment on the down-stream side of the core wall4 ,the extent of saturation of the outer bank varied greatly1 due to the difference in materials1 the care taken in building them1 and their ages4 ,fig4 #ai gives the average slopes of saturation as determined by these borings4 ,the experts stated that the slope of the surface of the saturation in the bank is determined by the solidity of the embankment3 ,the more compact the material of which the bank is built1 the steeper will be the slope of saturation4 ,as a result of their investigations1 the experts were of the opinion that the slope of saturation in the best embankments made of the material found in the ,croton ,valley is about #ce ft4 per #ajj ft41 and that with materials less carefully selected and placed the slope may be #bj ft4 per #ajj ft4 ,further1 that taking the loss of head in passing through the core wall1 and the slope assumed by the plane of saturation1 the maximum safe height of an earth dam with its top #bj ft4 above water level in the reservoir and its outside slope #b on #a1 is #fc to #ajb4e ft4 ,this is a remarkable finding in view of the fact that the ,titicus ,dam1 one of the ,croton ,valley dams examined1 has a maximum height above bed rock of #aaj ft4 and has been in use seven years4 ,this dam is not a fair example to cite in proof of their conclusion1 because its effective head is only about #df ft4#b ,illustration3 ,,bog ,,brook ,,dam4 ,illustration3 ,,middle ,,branch ,,dam4 ,,fig4 #ah4-;,,cross-,,section ,,of ,,two ,,croton ,,valley ,,dams1 ,,showing ,,saturation4 ,mr4 ,fteley gave as a reason for the elevation of the water slope found in the outer bank of the ,croton dams the fact of their being constructed of fine materials and stated that with comparatively porous materials they would have shown steeper slopes of saturation4 ,mr4 ,craven argued that all dams will absorb more or less water1 and that porosity is merely a degree of compactness2 that slope implies motion in water1 and that there is no absolute retention of water in the outer bank of a dam having its base below the plane indicated by the loss of head in passing through the inner bank and then through a further obstruction of either masonry or puddle2 that there is simply a partial retention1 with motion through the bank governed by the degree of porosity of the material4 ,fig4 #ai is a graphical interpretation of the conclusion reached by the board of experts1 as already given on page #da4 8,a0 is an ideal profile of a homogeneous dam with the inner slope #c on #a and the outer slope #b on #a4 ,the top width is made #be ft4 for a dam having #ij ft4 effective head1 the high-water surface in the reservoir being #aj ft4 below the crest of the dam4 ,this ideal profile is a fair average of all the earth dams of the world4 ,not having a core wall to augment the loss of head1 it fairly represents what might be expected of such a dam built of ,croton ,valley material1 compacted in the usual way4 ,it should be noted that the intersection of the plane of saturation with the rear slope of the dam at such high elevation as shown indicates an excessive seepage and a dangerously unstable condition4 ,preliminary ,study of ,profile for ,dam4 ,the preliminary calculations for designing a profile for an earth dam are simple and will here be illustrated by an example4 ,let us assume the following values3 a4 ,central height of dam1 #ajj ft4 b4 ,maximum depth of water1 #ij ft41 with surface #aj ft4 below crest of dam4 c4 ,effective head1 #ij ft4 d4 ,weight of water1 #fb4e lbs4 per cu4 ft4 e4 ,weight of material1 #abe lbs4 per cu4 ft4 f4 ,coefficient of friction1 #a4jj1 or equal to the weight4 g4 ,factor of safety against sliding1 #aj4 ,the width corresponding to the vertical pressure of #a ft4 is1 7#fb4e #aj7_/abe #e ft4 ,illustration ,illustration3 ,,fig4 #ai4-;,,graphical ,,interpretation ,,of ,,studies ,,of ,,board ,,of ,,experts ,,on ,,the ,,original ,,earth ,,portion ,,of ,,the ,,new ,,croton ,,dam4 ,the hydrostatic pressure per square foot at #ij ft4 depth is1 #fb4e #ij #e1fbe lbs4 ,the dam1 having a factor of safety of #aj1 must present a resistance of1 #e1fbe #aj #ef1bej lbs41 or #bh tons per square foot4 ,the theoretical width of bank corresponding to #ij ft4 head and a factor of #aj is shown by the dotted triangle 7,a-,b-,b7 to be #dej ft41 7,b1 ,fig4 #ai7 with slopes #b on #a4 ,to this must be added the width due to the height of crest above the water surface in the reservoir and the width of crest4 ,the former would be1 #b 7#b #aj7 #ej ft41 and the latter by ,trautwine's rule1 #b #bajj #bb ft41 giving a total base width of #ebb ft4 ,let us now assume that the slope of saturation may be #ce ft4 per #ajj ft4 ,we observe that this intersects the base #dj ft4 within the outer toe of the bank slope4 ,if the plane of saturation was #cc ft4 per #ajj1 it would just reach the outer toe4 ,it would be advisable to enlarge this section by adding a #aj-;ft4 berm at the #ej-;ft4 level1 having a slope not less than #c on #a for the up-stream face1 and two #ae-;ft4 berms on the down-stream face1 having slopes #b on #a4 ,the additional width of base due to these modifications in our profile amounts to #fe ft41 giving a total base width of #ehg ft41 and increasing the factor of safety from #aj to #ac4 ,it should be remembered that if the bank becomes saturated this factor of safety may be reduced #ej1 the coefficient of moist clay being #j4ej4 ,the loss of head due to a core wall of masonry1 as designed for the ,new ,croton ,dam1 was assumed by the board of experts to be #ba ft41 or #ag of the depth of water in full reservoir4 ,it has been stated by several authorities that the primary object of a masonry core wall is to afford a water-tight cut-off to any water of percolation which may reach it through the upper half of the embankment4 ,it appears that absolute water-tightness in the core wall is not obtained1 although the core walls of the ,croton dams are said to be 8the very best quality of rubble masonry that can be made40 ,mr4 ,w4 ,w4 ,follett1 who is reported to have had considerable experience in building earth dams1 and who has made some valuable suggestions thereupon1 is emphatic in saying1 that the junction of earth and masonry forms a weak point1 that either a puddle or masonry core in an earthen dam is an element of weakness rather than strength4 ,he also thinks the usual manner of segregating and depositing materials different in density and weight1 and thus subject to different amounts of settlement1 as bad a form of construction as could be devised4 ,core walls may prevent 8free passage of water0 and 8excessive seepage10 but are nevertheless of doubtful expediency4 ,earthwork ,slips and ,drainage4 ,mr4 ,john ,newman1 in his admirable treatise on 8,earthwork ,slips and ,subsidences upon ,public ,works10 classifies and enumerates slips as follows3 ,natural causes1 #g4 ,artificial causes1 #ca4 ,additional causes due to impounded water1 #g4 ,after describing each cause he presents #ci different means used to prevent such slips and describes methods of making repairs4 ,mr4 ,wm4 ,l4 ,strange has had such a large and valuable experience and has set forth so carefully and lucidly both the principles and practice of earth dam construction1 that the writer takes pleasure in again quoting him on the subject of drainage1 of which he is an ardent advocate4 ,he says that1 thorough drainage of the base of a dam is a matter of vital necessity1 for notwithstanding all precautions1 some water will certainly pass through the puddle4 ,it is at the junction of the dam with the ground that the maximum amount of leakage may be expected4 ,the percolating water should be gotten out as quickly as possible4 ,the whole method of dealing with slips may be summed up in one word-drainage4 ,the proper presentation of these two phases of our subject would in itself require a volume4 ,the interested reader is therefore referred to the different authorities and writers cited in ,appendix ,,ii4 ,jerome ,park ,reservoir ,embankments4 ,the ,jerome ,park reservoir is an artificial basin involving the excavation and removal of large quantities of soil1 and the erection of long embankments with masonry core walls1 partly founded on rock and partly on sand4 ,the plan and specifications call for an embankment #bj ft4 wide on top1 with both slopes #b on #a1 and provide for lining the inner slope with brick or stone laid in concrete1 and for covering the bottom with concrete laid on good earth compacted by rolling4 ,illustration3 ,section at ,sta4 #ii4 ,illustration3 ,section at ,sta4 #gfbj4 ,,fig4 #bj4-;,,graphical ,,exhibit ,,of ,,studies ,,of ,,jerome ,,park ,,reservoir ,,embankment4 ,wherever bed rock was not considered too deep below the surface the core walls were built upon it4 ,in other places the foundation was placed #h to #aj ft4 below the bottom of the reservoir and rested upon the sand4 ,it appears that the plans of the ,jerome ,park embankment were changed from their original design1 prior to the report of the board of experts1 on account of two alleged defects1 namely1 8cracks in the core wall0 and 8foundation of quicksand10 and incidentally on account of the supposed instability of the inner bank4 ,in describing the materials on which these embankments rest the experts remarked that all these fine sands are unstable when mechanically agitated in an excess of water1 and that they all settle in a firm and compact mass under the water when the agitation ceases4 ,that they are quite unlike the true quicksands whose particles are of impalpable fineness and which are 8quick0 or unstable under water4 ,fig4 #bj is a graphic exhibit of the results of tests made at 8,station #gf #bj10 and at 8,station #ii10 to determine the flow line of water in the sand strata underlying the embankment and bottom of the ,jerome ,park reservoir4 ,the experts reported that there was no possible danger of sliding or sloughing of the bank2 that the utmost that could be expected would be the percolation of a small amount of water through the embankment and the earth2 and that this would be carried off by the sewers in the adjacent avenues2 that a large expenditure to prevent such seepage would not be warranted nor advisable4 ,in concluding their report1 however1 they recommended changing the inner slope of #b on #a to #b on #a1 and doubling the thickness of the concrete lining at the foot of the slope to preclude all possibility of the sliding or the slipping of the inner bank in case of the water being lowered rapidly in the reservoir4 ,mr4 ,w4 ,r4 ,hill1 then chief engineer of the ,croton ,aqueduct ,commission1 favored extending the core walls to solid rock4 ,he took exception to the manner of obtaining samples of sand by means of pipe and force-jet of water1 claiming that only the coarsest sand was obtained for examination4 ,he did not consider fine sand through which three men could run a -in4 rod #ai and #bj ft4 to rock without use of a hammer1 very stable material upon which to build a wall4 ,north ,dike of the ,wachusett ,reservoir1 ,boston4 ,the ,north ,dike of the ,wachusett ,reservoir is another large public work in progress at the present time4 ,it is of somewhat unusual design and the preliminary investigations and experiments which led to its adoption are interesting in the extreme4#c ,the area to be explored in determining the best location for the dike was great1 and the preliminary investigations conducted by means of wash drill borings1 very extensive4 ,a total of #a1aca borings were made to an average depth of #hc ft41 the maximum depth being #bhf ft4 ,the materials were classified largely by the appearance of the samples1 though chemical and filtration tests were also made4 ,the plane of the ground water was from #ce to #ej ft4 below the surface1 and the action of the water-jet indicated in a measure the degree of permeability of the strata4 ,in addition to these tests experimental dikes of different materials1 and deposited in different ways1 were made in a wooden tank #f ft4 wide1 #h ft4 high and #fj ft4 long4 ,the stability of soils when in contact with water was experimented with1 as shown in ,fig4 #ba1 in the following manner3 ,an embankment 7,fig4 #ba7 was constructed in the tank of the material to be experimented with1 #b ft4 wide on top1 #f ft4 high1 with slopes #b on #a1 and water admitted on both sides to a depth of #e ft4 ,the top was covered with #d-;in4 planks #b ft4 long and pressure applied by means of two jack screws resting upon a cross beam on top of the planks4 ,with a pressure of three tons per square foot1 the #d-;in4 planks were forced down into the embankment a little more than #f ins41 resulting in a very slight bulging of the slopes a little below the water level4 ,immediately under the planks the soil became hard and compact4 ,a man's weight pushed a sharp steel rod1 -in4 in diameter1 only #f to #h ins4 into the embankment where the pressure was applied1 while outside of this area the rod was easily pushed to the bottom of the tank4 ,these results corroborate in a general way the practical experience of the author1 both in compressed embankments1 where he found it necessary to use a pick vigorously to loosen the material of which they were composed1 and in embankments made by merely dumping the material from a track1 in which case the earth is so slightly compressed that an excavation is easily made with a shovel4 ,illustration3 ,fig4 #ba4 ,illustration3 ,fig4 #bb4 ,illustration3 ,fig4 #bc4-;,,can ,,for ,,determining ,,frictional ,,resistance ,illustration3 ,fig4 #bd4 ,illustration3 ,fig4 #be4 ,,figs4 #ba ,,to #bd4-;,,experimental ,,dikes ,,and ,,cylinder ,,employed ,,in ,,studies ,,for ,,the ,,north ,,dike ,,of ,,the ,,wachusett ,,reservoir2 ,,and 7,,fig4 #be7 ,,cross-,,section ,,of ,,the ,,dike4 ,the difference in the coefficient of friction of the same material when dry and when wet greatly modifies the form of slope4 ,the harder and looser the particles1 the straighter will be the slope line in excavation and slips4 ,the greater the cohesion of the earth1 the more curved will be the slope1 assuming a parabolic curve near the top-the true form of equilibrium4 ,,rate ,,of ,,filtration4-,the rate of filtration through different soils was experimented with by forming a dike in the tank previously mentioned1 as shown in ,fig4 #bb4 ,the dike was made full #h ft4 high1 #g ft4 wide on top1 with a slope on the up-stream side of #b on #a1 and on the down-stream side #d on #a4 ,this gave a base width of #ee ft4 ,immediately over the top of the dike there was placed #c ft4 of soil to slightly consolidate the top of the bank and permit the filling of the tank to the top without overflowing the dike4 ,the water pressure in different parts of the dike was determined by placing horizontal pipes through the soil crosswise of the tank4 ,these pipes were perforated and covered with wire gauze1 being connected to vertical glass tubes at their ends4 ,the end of the slope on the down-stream side terminated in a box having perforated sides and filled with gravel1 thus enabling the water to percolate and filter out of the bank without carrying the soil with it4 ,when the soil was shoveled loosely into the tank1 without consolidation of any kind1 it settled on becoming saturated and became quite compact4 ,it took five days for the water to appear in the sixth gauge pipe near the lower end of the tank4 ,after the pressure1 which was maintained constant1 had been on for several weeks1 the seepage amounted to one gallon in #bb minutes4 ,when the soil was deposited by shoveling into the water1 the seepage amounted to one gallon in #cd minutes4 ,the relative filtering capacities of soils and sands were thought to be better determined by the use of galvanized iron cylinders of known areas4 ,fig4 #bc shows one of the cylinders4 ,these latter experiments confirmed those previously made at ,lawrence1 by ,mr4 ,allen ,hazen1 for the ,massachusetts ,state ,board of ,health4 ,they showed that the loss of head was directly proportioned to the quantity of water filtered and that the quantity filtered will vary as the square of the diameter of the effective size of the grains of the filtering material4#d ,the material classed as 8permeable0 at the ,north ,dike of the ,wachusett ,reservoir has an effective diameter of about #j4bj mm4 ,a few results are given in the following table3 ,amount of ,filtration in ,gallons per ,day1 ,through an ,area of #aj1jjj ,sq4 ,ft41 ,with a ,loss of ,head or ,slope of #a ft4 in #aj ft4 ,material4 ,unit ratios4 ,u4 ,s4 gallons4 7#a7 ,soil #a #eaj 7#b7 ,very fine sand #ad #g1bjj 7#c7 ,fine sand #agf #ij1jjj 7#d7 ,medium sand #ghd #djj1jjj 7#e7 ,coarse sand #d1cec #b1bjj1jjj ,to be sure that the accumulation of air in the small interstices of the soil was not the cause of the greatly reduced filtration through it1 another series of experiments was conducted in the wooden tank1 as shown in ,fig4 #bd4 ,a pair of screens was placed near each end of the tank1 filled with porous material1 sand and gravel1 and the #ej-;ft4 space between filled with soil4 ,the soil was rammed in #c-;in4 layers1 and special care taken to prevent water from following along the sides and bottom of the tank4 ,one end was filled with water to near the top1 while the other end gave a free outlet4 ,after this experiment had been continued for more than a month1 the amount of seepage averaged #a4g gallons per #bd hours1 or about #cb drops per minute4 ,filtration tests were also made through soil under #aej ft4 head1 or #e lbs4 per sq4 in41 with results not materially different1 it is stated1 from those already given4 ,the soil used in all these tests contained from #d to #h by weight of organic matter4 ,this was burned and similar tests made with the incinerated soil1 resulting in an increase of about #bj more seepage water4 ,,permanence ,,of ,,soils4-,this last material experimented with suggests the subject of permanence of soils4 ,this was reported upon separately and independently by ,mr4 ,allen ,hazen and ,prof4 ,w4 ,o4 ,crosby4 ,these experts agreed in their conclusion1 stating that the process of oxidation below the line of saturation would be extremely slow1 requiring many thousands of years for the complete removal of all the organic matter1 and that the tightness of the bank would not be materially affected by any changes which are likely to occur4 ,it has been remarked1 that of all the materials used in the construction of dams1 earth is physically the least destructible of any4 ,the other materials are all subject to more or less disintegration1 or change in one form or another1 and in earth they reach their ultimate and most lasting form4 ,in speaking of the ,north ,dike of the ,wachusett ,reservoir1 ,mr4 ,stearns remarked that1 it was evident by the application of ,mr4 ,hazen's formula for the flow of water through sands and gravels1 that the very fine sands found at a considerable depth below the surface would not permit enough water to pass through them if a dike of great width were constructed1 to cause a serious loss of water1 and it was also found that the soil1 which contained not only the fine particles or organic matter1 but also a very considerable amount of fine comminuted particles1 which the geologist has termed 8rock flour10 would be sufficiently impermeable to be used as a substitute for clay puddle4 ,fig4 #be shows the maximum section of the ,north ,dike with its cut-off trench4 ,the quantities and estimated cost of the completed structure are given in the table herewith3 --- ,cost --- ,per cent4 ,work4 ,quantities4 ,unit ,actual4 total4 7cu4 yds47 ,price4 ,soil #e1bej1jjj #j4je #bfb1ejj #cd4g ,cut-off trench #edb1jjj 4#bj #ajh1djj #ai4c ,borrowed earth and gravel #bjj1jjj 4#bj #dj1jjj ,slope paving #ej1jjj #b4bj #aaj1jjj #ad4f ,sheet-piling1 pumping1 etc4 #aag1jjj #ae4e ,engineering and preliminary investigations #abj1jjj #ae4i ------- ----- ,total cost #geg1ijj #ajj4j ,druid ,lake ,dam1 ,baltimore1 ,md4 ,another very interesting and instructive example of high earth dam construction is that of the ,druid ,lake ,reservoir embankment1 ,baltimore1 ,md4 ,this dam was built under the supervision of ,mr4 ,robt4 ,k4 ,martin4 ,construction was begun in #ahfd1 and the dam was finished in #ahgj4 ,mr4 ,alfred ,m4 ,quick1 present chief engineer of the water-works of the ,city of ,baltimore has given a very lucid description of this work in ,engineering ,news of ,feb4 #bj1 #aijb4 ,fig4 #bf is a cross-section of this dam1 showing the method of construction so clearly as to scarcely need further description4 ,the banks ,d-,d on either side of the central puddle wall were carried up in #f-;in4 layers with horses and carts1 and kept about #b ft4 higher than the puddle trench1 which always contained water4 ,the banks ,e-,e were made of dumped material1 after which the basins ,f-,f were first filled with water and finally filled by dumping material into the water from tracks being moved in toward the center4 ,illustration3 ,,fig4 #bf-,,working ,,cross-,,section ,,of ,,druid ,,lake ,,dam4 ,after reaching the top of this fill1 banks ,b-,b-,b were built up in layers similar to ,d-,d4 ,the second set of basins ,c-,c were then filled in a manner similar to ,f-,f4 ,the remaining portion ,a-,a was constructed in layers like ,d-,d and ,b-,b1 with the addition of compacting each layer with a heavy roller4 ,finally the inner face slope was carried up in #c-;in4 layers and thoroughly rolled1 after which #b ft4 of 8good puddle0 was put upon the inner slope the latter was rip-rapped1 the crown covered with gravel and the rear slope sodded4 ,some years after completion1 a driveway was built along the outer slope1 as shown1 which had a tendency to strengthen the dam1 though not designed expressly for that purpose4 ,it is of interest to know that the influent1 effluent and drain pipes were originally constructed through or under the embankment4 ,these pipes were laid upon solid earth1 and where they passed through the puddle wall were supported upon stone piers #f ft4 apart4 ,as might be expected1 they soon cracked badly and were finally abandoned1 new ones being placed in the original ground at the south side of the lake4 ,mr4 ,quick states that so far as is known there has never been any evidence of a leak through the embankment during these #cb years of service4 ,new ,types of ,dams2 ,bohio1 ,panama ,canal4 ,a brief description will now be given of three different dams designed for ,bohio1 on the proposed ,panama ,canal4 ,mr4 ,george ,s4 ,morison's paper before the ,american ,society of ,civil ,engineers1 on 8,the ,bohio ,dam10 and the discussion thereon1 especially that by ,mr4 ,f4 ,p4 ,stearns1 were quite fully reported in ,engineering ,news for ,march #ac and ,may #h1 #aijb4 ,in constructing the ,panama ,canal it will be necessary to impound the waters of the ,chagres ,river1 near ,bohio1 to maintain the summit level of this canal and supply water for lockage4 ,,the ,,french ,,design4-,fig4 #bg is an enlarged section of the original design of the new ,french ,co4 ,this design has no core wall1 but at the up-stream toe a concrete wall was to be built across the river between the two lines of sheet-piling4 ,at the down-stream toe a large amount of riprap was to be placed to prevent destruction of the dam during construction4 ,in this case it would be necessary to construct a temporary dam above and also to use the excavation for the locks as a flood spillway4 ,this method would involve considerable risk to the work1 on account of the large volume of flood waters it might be necessary to take care of during construction4 ,,isthmian ,,canal ,,commission4-,the dam proposed by the ,isthmian ,canal ,commission is shown by ,fig4 #bh4 ,this was designed to be an absolutely water-tight closure of the geological valley1 by using a masonry core wall carried down to bed rock4 ,the maximum depth being #abi ft41 it was planned to rest the concrete wall on a series of pneumatic caissons reaching to rock4 ,the spaces between the caissons would be closed and made water-tight4 ,both slopes of the earth embankment were to have horizontal benches and be revetted with loose rock4 ,,mr4 ,,morison',s ,,design4-,to appreciate fully the object and aim of the third design1 ,fig4 #bi1 which may be called a new type1 although similar in many respects to the ,north ,dike of the ,wachusett reservoir already illustrated and described1 it should be stated that the equalized flow of the ,chagres ,river is put at #a1jjj cu4 ft4 per sec4 ,of this quantity it is estimated that #ejj cu4 ft4 would be needed for lockage and #bjj cu4 ft4 for evaporation4 ,this leaves #cjj cu4 ft4 per sec4 available for seepage and other losses or to be wasted4 ,illustration ,illustration ,illustration3 ,,figs4 #bg ,,to #bi4-;,,designs ,,for ,,the ,,bohio ,,dam1 ,,panama ,,canal4 ,it will thus be seen that a scarcity of water is not in this instance a condition demanding an absolutely water-tight dam4 ,the amount of seepage permissible without endangering the stability of the structure is the real point now to be discussed4 ,the third design1 which was proposed by ,mr4 ,morison1 is shown by ,fig4 #bi4 ,the topography and configuration of this dam site is not unlike that of the ,san ,leandro ,dam1 ,california1 soon to be described1 while the general design is similar1 as has been remarked1 to the ,north ,dike of the ,wachusett ,reservoir4 ,this third design contemplates a compound structure1 formed by two rock-fill dams situated about #b1abj ft4 apart1 with the intervening space filled with loose rock1 earth and other available material4 ,immediately below the upper and higher rock-fill dam1 it is proposed to place across the canyon a puddle wall #ej ft4 in width1 resting over two lines of sheet-piling #cj ft4 apart4 ,this piling would probably not reach farther than #ej ft4 below tidewater1 the solid rock floor being about #ajj ft4 deeper4 ,mr4 ,morison made use of ,mr4 ,hazen's filtration formula for estimating the rate and quantity of seepage through the permeable strata below the dam4 ,this formula is3 h t #aj ,v cd -- ------ l #fj where ,v rate of flow in meters per day through the whole section4 c constant varying from #dej to #a1bjj1 according to cleanness of the sand4 d 8effective size0 of sand in mm4 h head in feet4 l length or distance water must pass4 t temperature of the water 7,fahr47 ,this formula should be used only when the effective sizes of sands are from #j4aj to #c4j mm4 and with uniformity coefficients below #e4je4 ,mr4 ,morison used the following values3 c #a1jjj2 d #a4j mm42 h #ij ft42 l #b1ejj ft42 t #ij2 for the solution of this problem1 and obtained a velocity of #j4jjb ft4 per sec4 ,the bed of sand and gravel was assumed to have a sectional area of #bj1jjj sq4 ft4 for #b1ejj ft4 in length4 ,this gives a seepage of #dj cu4 ft4 per sec4 ,it is believed that the above rate of #j4jjb ft4 per sec41 equivalent to #a ins4 per minute1 or #g ft4 per hour1 is not sufficient to move any of the material4 ,the velocity of water percolating through sand is found to vary directly as the head and inversely as the distance4 ,the value of 8c0 in the formula is larger for sands of filters favorable for flow1 and smaller for compacted materials and dams4 ,mr4 ,morison thought it might be nearer the actual conditions to assume d #j4ej mm42 c #ejj2 and l #e1jjj ft42 in which case the seepage would only amount to #b4e ft4 per sec4 ,in this last assumption the 8effective size0 of sand grains is #b times that classed as 8permeable material0 at the ,north ,dike of the ,wachusett ,reservoir4 ,prof4 ,philipp ,forchheimer1 of ,gratz1 ,austria1 recommends the use of the formula1 h --- a b l for the percolation through soils between loam and loamy sand4 ,sellheim1 ,masoni1 ,smreker1 ,krber and other authorities on filtration use still other formulas1 to which the reader and student is referred for further research4 ,the writer1 having had occasion in his professional practice to study quite carefully the subject of ground waters1 and their percolation or flow through different classes of materials and under varying conditions1 is of the opinion that rarely does the cross-section of a stream-channel1 filled with sand1 gravel and debris1 present1 even approximately1 a homogeneous or uniform mass2 and that there are1 almost without exception1 strata of material much coarser and more porous than the general average4 ,in other words1 that it is extremely difficult to arrive at a uniformity coefficient4 ,it is unwise to place much reliance upon an estimated flow where this is the case4 ,the formula may be used with confidence where the layers are artificially made1 and where there is no uncertainty regarding the uniform character of the material4 ,in most natural channels there are distinct lines of flow1 and under considerable hydrostatic head or pressure these lines of flow would surely enlarge4 ,there is a wide difference between permissible and dangerously excessive percolation through an earth embankment4 ,the local features1 economical considerations and magnitude of the risks1 all bear upon this question and must be considered for each particular case4 ,it is of interest to compare the estimated cost of the three designs proposed for the ,bohio ,dam1 based upon the same unit prices1 as follows3 ,french ,engineers' design #c1ejj1jjj ,isthmian ,canal ,commissioners' design #h1jjj1jjj ,mr4 ,morison's design #b1ejj1jjj ,no comments will be made upon these figures1 further than to remark that the successful building of a stable dam1 accomplished by the use of an excessive quantity of materials and at a cost beyond reasonable requirements1 is mainly instructive as illustrating 8how not to do it40 ,it is creditable to execute substantial works at a reasonable cost1 but it reflects no credit upon any one to construct them regardless of expense4 ,combined ,rock-fill and ,earth ,dam4 ,fig4 #cj shows a section of the ,upper ,pecos ,river ,dam near ,eddy1 ,n4 ,m4 ,this dam is quite fully described by ,mr4 ,jas4 ,d4 ,schuyler1 in his recent book on 8,reservoirs for ,irrigation1 ,water-,power and ,domestic ,water-,supply10 and need not be mentioned in this paper1 further than to call attention to the combination of rock-fill and earth which constitutes its particular type of construction4 ,this type of dam is believed to be for many localities a very good one1 but up to the present time has only been adopted for dams of moderate height1 under #fj ft4 ,the ,san ,leandro ,dam1 ,california4 ,a section of the ,san ,leandro ,dam1 near ,oakland1 ,cal41 is shown by ,fig4 #ca4 ,this section was supplied by ,mr4 ,w4 ,f4 ,boardman1 hydraulic engineer1 who superintended the construction of the dam1 from his own private notes and data4 ,it differs materially from sections heretofore published1 and is #e ft4 higher1 thus making it rank as the highest earth dam in the world of which we have an authentic record4 ,the dam was commenced in #ahgd1 and brought up to a height of #aae ft4 above the bed of the creek in #ahih4 ,at the present time it is #ejj ft4 in length on the crest and #bh ft4 wide4 ,the original width of the ravine at the base of the dam was #ff ft4 ,the present width of base from toe to toe of slopes is #a1gjj ft4 ,the height of embankment above the original surface is #abe ft41 with a puddle trench extending #cj ft4 below4 ,illustration3 ,,fig4 #cj4-;,,cross-,,section ,,of ,,upper ,,pecos ,,river ,,dam2 ,,combined ,,rock ,,fill ,,and ,,earth4 ,illustration3 ,,fig4 #ca4-;,,developed ,,section ,,of ,,san ,,leandro ,,dam4 ,all that portion of the dam within a slope of #b on #a at the rear and #c on #a at the face is built of choice material1 carefully selected and put in with great care4 ,the portion outside of the #b on #a slope line at the down-stream side of the dam1 was sluice in from the adjacent hills regardless of its character1 and is composed of ordinary soil containing more or less rock4 ,this process of sluicing was carried on during the rainy season1 when there was an abundance of water1 and it was intended to be continued until the canyon below the dam had been filled to an average slope of #f4g on #a at the rear of the dam4 ,it was thought that the location was particularly favorable for this kind of construction1 the original intention being to raise the dam from time to time1 not only to increase the storage as the demand for water increased1 but to meet the annual loss in capacity caused by the silting up of the reservoir basin4 ,the latter has amounted to about #a ft4 in depth per annum4 ,,method ,,of ,,construction4-,under the main body of the dam1 the surface was stripped of all sediment1 sand1 gravel and vegetable matter4 ,choice material1 carefully selected1 was then brought by carts and wagons and evenly distributed over the surface in layers about #a ft4 or less in thickness4 ,this was sprinkled with just enough water to make it pack well1 not enough to make it like mud4 ,during construction a band of horses was led by a boy on horseback over the entire work1 to compact the materials and assist in making the dam one homogeneous mass4 ,no rollers were used on this dam4 ,the central trench was cut #cj ft4 below the original bed of the creek4 ,in the bottom of this trench three secondary trenches1 #c ft4 wide by #c ft4 deep1 were made and filled with concrete4 ,these concrete walls were carried up #b ft4 above the general floor of the trench1 to break the continuity of its surface4 ,the original wasteway1 constructed at the north end of the dam1 has been practically abandoned1 having been substituted by a tunnel of larger capacity4 ,the original wasteway was excavated in the bed rock of the natural hillside1 and although lined with masonry1 is not in the best condition4 ,the author considers its location an objectionable feature1 as menacing the safety of the dam1 and thinks it should be permanently closed4 ,a wasteway tunnel1 #a1dhg ft4 in length1 was constructed in #ahhh1 through a ridge extending north of the dam4 ,this has a sectional area of about #ajaj ft41 lined with brick masonry throughout1 having a grade of #b4 ,the criticism might be made of the tunnel that it is faulty in design at the entry or reservoir end1 where the water must first fall over a high spillway wall1 aerating the water before entering the tunnel proper4 ,the water even then has not easy access to the tunnel1 and no adequate arrangements have been made for ventilation1 so as to insure the utilization of its maximum capacity4 ,the maximum depth of water in the reservoir is about #he ft41 and the full capacity #fhi1jjj1jjj cu4 ft4 of water4 ,the catchment area is #dc square miles1 and the surface of the reservoir when full #dcf acres4 ,the outlet pipes are placed in two tunnels at different elevations through the ridge north of the dam4 ,there are no culverts or pipes extending through the body of the dam itself4 ,hydraulic-fill ,dams4 ,no discussion of earth dams would be complete without some reference being made to the novel type of construction developed in western ,america in recent years1 by which railroad embankments and water-tight dams are built up by the sole agency of water4 ,the water for this purpose is usually delivered under high pressure1 as it is generally convenient to make it first perform the work of loosening the earth and rock in the borrow pit1 as well as subsequently to transport them to the embankment1 and there to sort and deposit them and finally part company with them after compacting them solidly in place1 even more firmly than if compressed by heavy rollers4 ,sometimes1 however1 water is delivered to the borrow pit without pressure1 in which event the materials must be loosened by the plow or by pick and shovel by the process called ground sluicing in placer mining parlance4 ,an abundance of water delivered by gravity under high pressure is usually regarded as one of the essential factors in hydraulic-fill dam building1 but it is not essential that there be a large continuous flow4 ,the ,lake ,frances ,dam1 recently constructed for the ,bay ,counties ,co41 of ,california1 by ,j4 ,d4 ,schuyler1 is #ge ft4 high1 #a1cdj ft4 long on top1 and contains #bhj1jjj cu4 yds4 ,the dam was built up by materials sluiced by water that was forced by a centrifugal pump through a #ab-;in4 pipe and #c-;in4 nozzle1 against a high bank1 whence the materials were torn and conveyed by the water through flumes and pipes to the dam4 ,about #f cu4 ft4 per sec4 of water was thus used1 and at one stage of the work the supply stream was reduced to less than #j4a ft4 per sec41 the water being gathered in a pond and pumped over and over again4 ,the chapter on hydraulic-fill dams in ,mr4 ,schuyler's book on 8,reservoirs for ,irrigation0 will be found to contain matter on the subject interesting to those who desire to pursue it further1 and the reader is again referred to that work4 ,an ,impervious ,diaphragm in ,earth ,dams4 ,as a result of the recent extended discussion concerning the design of the ,new ,croton ,dam and the ,jerome ,park ,reservoir embankments1 the ,engineering ,news of ,feb4 #bj1 #aijb1 contained a very suggestive editorial entitled1 8,concerning the ,design of ,earth ,dams and ,reservoir ,embankments40 ,the opinion is given that no type of structure that man builds to confine water can compare in permanence with earth dams1 after which the following pertinent questions are asked3 #a4 ,how shall an earth dam be made water-tight8 #b4 ,what is the office and purpose of the masonry core wall8 #c4 ,would not a water-proof diaphragm of some kind be better than a core wall of either masonry or puddle8 ,the article then suggests a number of designs of diaphragm construction1 with a special view of obtaining absolute water-tightness1 by use of asphaltum1 cement mortar1 steel plates1 etc4 ,special emphasis was put upon the principle of constructing a water-proof diaphragm4 ,the matter of relative cost is advanced as an argument in favor of the diaphragm principle as against the usual orthodox method4 ,the saving in cost is to be accomplished by the use of inferior materials and less care in the handling of them1 or by both4 ,it is suggested that almost any kind of material available1 rock1 sand or gravel1 will answer every purpose where good earth is not to be found4 ,further1 that this material may be dumped from the carts1 cars or cableways1 or be placed by the hydraulic-fill method4 ,the writer believes the diaphragm method of construction may have some merits1 but that it is attended by the very great risk of neglecting principles most vitally important to the successful construction of high earth dams1 which will now be formulated and advanced1 as follows3 ,,chapter ,,vi4 ,conclusions4 ,the writer in concluding this study wishes to emphasize certain principles and apparently minor details of construction1 which from observation and personal experience1 seem to him of vital importance4 ,he believes firmly in the truth contained in the following remarks by ,mr4 ,desmond ,fitz,gerald1 of ,boston1 germane to this subject3 ,an engineer must be guided by local conditions and the resources at his command in building reservoir embankments4 ,his design must be largely affected by the nature of the materials4 ,there are certain general principles1 however1 which must be observed and which will be applied by an engineer of skill1 judgment and experience to whatever design he may adopt4 ,it is in the application of these principles that the services of the professional man becomes valuable1 and it is from a lack of them1 that there have been so many failures4 ,the details and principles of construction1 relating to high earth dams1 may be summarized or stated in order of their application1 as follows3 7#a7 ,select a firm1 dry1 impermeable foundation1 or make it so by excavation and drainage4 ,all alluvial soil containing organic matter and all porous materials should be excavated and removed from the dam site when practicable2 that is1 where the depth to a suitable impermeable foundation is not prohibitive by reason of excessive cost4 ,wherever springs of water appear1 they must be carried outside the lines of the embankment by means of bed rock drains1 or a system of pipes so laid and embedded as to be permanent and effective4 ,the drainage system must be so designed as to prevent the infiltration of water upward and into the lower half of the embankment1 and at the same time insure free and speedy outlet for any seepage water passing the upper half4 ,all drains should be placed upon bed rock or in the natural formation selected for the foundation of the superstructure4 ,they should be constructed in such a manner as to prevent the flow of water outside the channel provided for it1 and also prevent any enlargement of the channel itself4 ,to this end1 cement1 mortar1 broken stone1 and good gravel puddle are the materials best suited for this purpose4 7#b7 ,unite the body of the embankment to the natural foundation by means of an impervious material1 durable and yet sufficiently elastic to bond the two together4 ,when the depth to a suitable foundation is great1 a central trench excavated with sloping sides1 extending to bed rock or other impervious formation1 refilled with good puddling material1 properly compacted1 will suffice4 ,when clayey earth is scarce and expensive to obtain1 a small amount of clay puddle confined between walls of brick1 stone or concrete masonry1 and extending well into the body of the embankment and so built as to avoid settlement1 will prevent excessive seepage4 ,this form of construction is not to be carried much above the original surface of the ground4 7#c7 ,the continuity of surfaces should always be broken1 at the same time avoiding the formation of cavities and lines of cleavage4 ,no excavation to be refilled should have vertical sides1 and long continuous horizontal planes should be intercepted by wedge-shaped offsets1 enabling the dovetailing of materials together4 ,all loose and seamy rock or other porous material should be removed1 and where the refill is not the best for the purpose1 mix the good and bad ingredients thoroughly1 after which deposit in very thin layers4 7#d7 ,make the dimensions and profile of dam with a factor of safety against sliding of not less than ten4 ,the preliminary calculations for designing such a profile have been given on p4 #db4 7#e7 ,aim at as nearly a homogeneous mass in the body of the embankment as possible1 thus avoiding unequal settlement and deformation4 ,this manner of manipulating materials will eliminate many uncertain or unknown factors1 but it means rigid inspection of the work and intelligent segregation of materials1 no matter what method of transporting them may be adopted4 ,the smaller the unit loads may be1 the more easily a homogeneous distribution of materials will be obtained4 7#f7 ,select earthy materials in preference to organic soils1 with a view of such combination or proportion of different materials as will readily consolidate4 ,consolidation is the most important process connected with the building of an earth dam4 ,the judicious use of soil containing a small percentage of organic matter may be permitted1 however1 when there is a lack of clayey material for mixing with sandy and porous earth materials4 ,such a mixture1 properly distributed and wetted1 will consolidate well under heavy pressure and prove quite satisfactory4 7#g7 ,consolidation being the most important process and the only safeguard against permeability and instability of form1 use only the amount of water necessary to attain this4 ,too much or too little are equally bad and to be avoided4 ,it is believed that only by experiment and experience is it possible to determine just the proper quantity of water to use with the different classes of materials and their varying conditions4 ,in rolling and consolidating the bank1 all portions that have a tendency to quake must be removed at once and replaced with material that will consolidate2 it must not be covered up1 no matter how small the area4 7#h7 ,in an artificial embankment for impounding water it is impracticable to place reliance upon time for consolidation2 it must be effected by mechanical means4 ,again we repeat1 that consolidation is the most vitally important operation connected with the building of an earth dam4 ,when this is satisfactorily attained it is proof that the materials are suitable and that the other necessary details have been in a large measure complied with4 ,light rollers are worse than useless1 being a positive harm1 resulting in a smoothing or 8ironing process10 deceptive in appearance and detrimental in many ways4 ,the matter of supreme importance in the construction of earth dams is that the greatest consolidation possible be specified and effected4 ,to this end it is necessary that heavy rollers be employed1 and that such materials be selected as respond best to the treatment4 ,there are certain kinds of earth materials which no amount of wetting and rolling will compact4 ,these must be rejected as unfit for use in any portion of an earth dam4 ,let the design of the structure be ever so true to correct engineering principles1 it is still necessary to give untiring attention to the work of consolidation4 ,it is therefore according to the design of a thoroughly compacted homogeneous mass1 rather than to the suggested diaphragm type1 to which modern practice should conform4 ,this is in harmony with ,nature's own methods1 and in conformity to correct principles4 7#i7 ,avoid placing pipes or culverts through any portion of the embankment4 ,the writer considers it bad practice ever to place the outlet pipes through a high earth dam1 and fails to see any necessity for so doing4 7#aj7 ,the surface of the dam1 both front and rear1 must be suitably protected against the deteriorating effects of the elements4 ,this may include pitching the up-stream face1 the riprap work at the toe of the inner slope1 the roadway and covering of the crown1 the sodding or other protection of the rear slope1 and the construction of surface drains for the berms4 7#aa7 ,ample provision for automatic wasteways should be made for every dam1 so that the embankment can never under any circumstances be over-topped by the impounded water4 ,earthquakes and seismic disturbances will produce no disastrous effects upon an earth dam4 ,its elasticity will resist the shock of water lashing backwards and forwards in the reservoir4 7#ab7 ,finally1 provide for intelligent and honest supervision during construction1 and insist upon proper care and maintenance ever afterwards4 ,,appendix ,i4 ,high ,earth ,dams4 -,embankment- --- ,slopes --- ,available ,name of ,dam ,max4 ,top depths1 or ,reservoir4 ,location4 height1 width1 ,water4 ,bear4 ft4 ft4 ft4 ,san ,leandro ,california #abe #bh ,tabeaud ,california #abc #bj #c on #a #b on #a #gj ,druid ,hill ,maryland #aai #fj #d on #a #b on #a #hb ,dodder ,ireland #aae #bb #c on #a #c on #a ,titicus ,dam ,new ,york #aaj #cj #b on #a #b on #a ,mudduk ,tank ,india #ajh #c on #a #b on #a ,cummum ,tank ,india #ajb #c on #a #a on #a #ij ,dale ,dike ,england #ajb #ab #b on #a #b on #a ,marengo ,algeria #aja ,torside ,england #ajj #hd ,yarrow ,england #ajj #bd #c on #a #b on #a ,honey ,lake ,california #if #bj #c on #a #b on #a ,pilarcitos ,california #ie #be #b on #a #b on #a ,san ,andres ,california #ie #be #c on #a #c on #a ,temescal ,california #ie #ab #c on #a #b on #a ,waghad ,india #ie #f #c on #a #b on #a #ha ,bradfield ,england #ie #ab #b on #a #b on #a ,oued ,menrad ,algeria #ie ,st4 ,andrews ,ireland #ic #be ,edgelaw ,scotland #ic #c on #a #b on #a ,woodhead ,england #ij #gb ,tordoff ,scotland #he #aj #c on #a #b on #a ,naggar ,india #hd ,vahar ,india #hd #bd #c on #a #b on #a ,rosebery ,scotland #hd ,atlanta ,georgia #hb #dj ,roddlesworth ,england #hj #af #c on #a #b on #a #fh ,gladhouse ,scotland #gi #ab #c on #a #b on #a #fh ,rake ,england #gh #c on #a #b on #a ,silsden ,england #gh #c on #a #b on #a ,glencourse ,scotland #gg #c on #a #eh ,leeshaw ,england #gg ,wayoh ,england #gf #bb #c on #a #b on #a ,ekruk ,tank ,india #gf #bj #c on #a #b on #a #fe ,nehr ,india #gd #h ,middle ,branch ,new ,york #gc ,leeming ,ireland #gc #aj #c on #a #b on #a #ej ,south ,fork ,penna4 #gb #bj #b on #a #a on #a #ej ,anasagur ,india #gj #bj #d on #a ,pangran ,india #fh #h #db ,harlaw ,scotland #fg #fd ,lough ,vartry ,ireland #ff #bh #c on #a #b on #a #fj ,la ,mesa ,california #ff #bj #a on #a #a on #a #fj ,amsterdam ,new ,york #fe ,mukti ,india #fe #aj #c on #a #b on #a #da ,snake ,river ,california #fd #ab #b on #a #a on #a ,stubken ,ireland #fc #bd #c on #a #b on #a ,den of ,ogil ,scotland #fj #ej ,loganlea ,scotland #ei #aj #c on #a #b on #a #ee ,ashti ,india #eh #f #c on #a #b on #a #db ,cedar ,grove ,new ,jersey #ee #ah #c on #a #b on #a #ej ,,appendix--,,ii4 ,works of ,reference4 ,author4 ,title4 ,date4 ,baker1 ,benj4 ,the ,actual ,lateral ,pressure of ,earthwork #ahha ,baker1 ,ira ,o4 ,treatise on ,masonry ,construction #ahii ,bell1 ,thos4 ,j4 ,history of the ,water ,supply of the ,world #ahhb ,beloe1 ,chas4 ,h4 ,beloe on ,reservoirs #ahgb ,bowie1 ,aug4 ,j41 ,jr4 ,a ,practical ,treatise on ,hydraulic ,mining #ahih ,brant1 ,wm4 ,j4 ,scientific ,examination of ,soils #ahib ,brightmore1 ,a4 ,m4 ,the ,principles of ,water-,works ,engineering #ahic ,buckley1 ,robt4 ,b4 ,irrigation ,works in ,india and ,egypt #ahic ,cain1 ,wm4 ,retaining ,walls #ahhh ,chittenden1 ,h4 ,m4 ,report and ,examination of ,reservoir ,sites in ,wyoming and ,colorado #ahih ,courtney1 ,c4 ,f4 ,masonry ,dams #ahig ,fanning1 ,j4 ,t4 ,water-,supply ,engineering #ahhi ,flynn1 ,p4 ,j4 ,irrigation ,canals and ,other ,irrigation ,works #ahib ,frizell1 ,jos4 ,p4 ,water ,power #ahia ,gordon1 ,h4 ,a4 ,mining and ,mining ,engineering #ahid ,gould1 ,e4 ,s4 ,the ,elements of ,water-,supply ,engineering #ahii ,hall1 ,wm4 ,ham4 ,irrigation in ,california #ahhh ,hazen1 ,allen ,the ,filtration of ,public ,water ,supplies #ahie ,howe1 ,m4 ,a4 ,retaining ,walls for ,earth #ahia ,hughes1 ,saml4 ,treatise on ,water-,works #ahef ,jackson1 ,l4 ,d4 ,a4 ,statistics of ,hydraulic ,works #ahhe ,kirkwood1 ,j4 ,p4 ,filtration of ,river ,waters #ahfi ,merriman1 ,m4 ,treatise on ,hydraulics1 ,masonry ,dams and ,retaining ,walls #ahib ,newell1 ,f4 ,h4 ,irrigation in the ,united ,states #aijb ,newman1 ,john ,earthwork ,slips and ,subsidences ,upon ,public ,works #ahij ,potter1 ,thomas ,concrete #ahid ,schuyler1 ,j4 ,d4 ,reservoirs for ,irrigation1 ,water ,power and ,domestic ,water ,supply #aija ,slagg1 ,chas4 ,water ,engineering #ahhh ,stearns1 ,f4 ,p4 ,metropolitan ,water-,works ,reports #ahig ,stockbridge1 ,h4 ,e4 ,rocks and ,soils #ahhh ,trautwine1 ,j4 ,c4 ,earthwork2 and ,engineer's ,pocket-,book #ahij ,turner1 ,j4 ,h4 ,t4 ,the ,principles of ,water-,works ,engineering #ahic ,wilson1 ,j4 ,m4 ,manual of ,irrigation ,engineering #ahic ,annual ,reports4 ,massachusetts ,state ,board of ,health4 ,geological ,survey of ,new ,jersey4 ,metropolitan ,water-,works1 ,boston and vicinity4 ,u4 ,s4 ,geological ,survey4 ,transactions ,american ,society of ,civil ,engineers4 ,vols4 #c1 #ae1 #bd1 #cb1 #cd and #ce4 ,proceedings of the ,institution of ,civil ,engineers4 ,vols4 #ei1 #fb1 #fe1 #ff1 #ga1 #gc1 #gd1 #gf1 #hj1 #aae and #acb4 ,engineering ,news4 ,vols4 #ai to #df4 ,engineering ,record4 ,vols4 #bc to #df4 ,journal of the ,association ,engineering ,societies4 ,vol4 #ac4 ,,index4 ,analyses1 soil1 ,tabeaud ,dam1 #be ,analyses of soils1 #ad ,tabeaud ,dam1 #be ,borings1 wash drill1 ,wachusett ,dam1 #dh ,catchment area1 #c ,clay for puddle1 #ae ,contractors' outfit1 ,tabeaud ,dam1 #ca ,core wall1 impervious diaphragm as substitute for1 #fb necessity for1 #dd 7,see puddle47 ,dam1 ,ashti1 ,india1 #ce ,bog ,brook1 #da ,bohio1 ,panama ,canal1 #ed ,croton ,valley1 slope of saturation in1 #dj different types of earth1 #cc ,druid ,lake1 ,baltimore1 #eb high earth1 statistical table of1 #fg hydraulic-fill1 #fa hydraulic-fill1 ,san ,leandro1 #fj ideal profile of1 #db ,isthmian ,canal ,commission1 #ed ,lake ,frances hydraulic-fill1 #fa ,new ,croton1 #ci graphical study of original earth portion of1 #dc ,new ,england1 typical section of1 #dj new types of1 #ed ,north ,dike1 ,wachusett ,reservoir1 #dh rock-fill and earth combined1 upper ,pecos ,river1 #eh safe height of1 #ci ,san ,leandro1 #eh site location1 #g ,tabeaud1 #ac1 #ag ,titicus1 #da ,upper ,pecos ,river rock-fill and earth1 #eh with puddle core wall or face1 #cc ,yarrow1 ,liverpool water-works1 #i1 #cc ,diaphragms impervious for earth dams1 #fb1 #fe ,dike1 north of ,wachusett ,reservoir 7see ,dam2 also reservoir7 ,drainage and slips of earthwork1 #de of dam sites1 #fc ,drains1 bed rock1 ,tabeaud ,dam1 #ai ,earthwork slips and drainage1 #de ,embankment1 ,ashti1 ,india1 #ce ,embankments1 ,jerome ,park ,reservoir1 #de1 #df ,factor of safety for dams1 #fd ,filtration1 experiments on nitration through soils at ,wachusett ,reservoir1 #ej formula1 ,hazen's1 #ef ,foundations1 #i1 #fc ,gravel for puddle1 #ae ,infiltration and percolation1 #ch ,isthmian ,canal ,commission1 designs of dams for1 #ed ,outlet pipes and tunnels1 #f ,percolation1 #ch1 #eg ,profile1 ideal for dams1 #db ,puddle1 #ad core wall1 ,ashti ,dam1 #ce or face1 #cc trench1 #cg wall1 ,druid ,lake ,dam1 #ec for ,yarrow ,dam1 #cd vs4 puddle face1 #cg ,reservoir basin1 #cg outlets1 #f ,wachusett1 #dh ,rollers for dams1 #cj1 #fe ,sands and gravels1 flow of water through1 #eb 7,also see percolation47 ,slips and drainage of earthwork1 #de ,soil analyses1 ,tabeaud ,dam1 #be analysis1 #ad ,soils1 experiments on filtration through at ,wachusett ,reservoir1 #ej outline study of1 #ab permanence of1 #ea selection of1 for dams1 #fd studies1 ,wachusett ,reservoir1 #ej ,spillway or wasteway1 #h ,tabeaud ,dam1 #ca ,subsidences1 earthwork1 #de ,test pits1 #e1 #h1 #i ,tunnel1 outlet1 ,tabeaud ,dam1 #cj ,tunnels as outlets to reservoirs1 #f ,wasteway or spillway1 #h1 #ff ,tabeaud ,dam1 #ca ,,footnotes3 #a ,the writer had intended to present a table of physical properties of different materials1 giving their specific gravity1 weight1 coefficient of friction1 angle of repose1 percentage of imbibition1 percentage of voids1 etc41 but found it impossible to harmonize the various classifications of materials given by different authorities4 #b ,the effective head at any point of an earth dam has been defined as the difference in the elevation of the high-water surface in the reservoir and that of the intersection of the down-stream slope with the natural or restored surface of the ground below the dam4 #c ,this work is very fully described in the ,annual ,reports of the ,metropolitan ,water ,board of ,boston2 and by ,mr4 ,f4 ,p4 ,stearns1 ,chief ,engineer of the ,metropolitan ,water and ,sewerage ,board1 in the ,proceedings of the ,american ,society of ,civil ,engineers for ,april1 #aijb4 ,the latter description was reprinted1 with the omission of some of the illustrations1 in ,engineering ,news for ,may #h1 #aijb4 #d ,by effective size of sand grains is meant such size of grain that #aj by weight of the particles are smaller1 and #ij larger than itself2 or1 to express it a little differently1 the effective size is equal to a sphere the volume of which is greater than _/ that forming the weight and is less than _/ that forming the weight4 #e ,the term 8uniformity coefficient0 is used to designate the ratio of the size of the grain which has #fj of the sample finer than itself to the size which has #aj finer than itself4 ,the method of determining the size of sand grains and their uniformity coefficients1 is fully explained in ,appendix #c of ,mr4 ,hazen's book on 8,the ,filtration of ,public ,water ,supplies40