\ A mm H l I | 117 AN EXPERIMENTAL STUDY OF MATERIALS USED IN STRUCTURAL BACKFILLS Thesis for the Degree of .3. S. HICHTGAN STATE COLLEGE Warren William McNicol 1946 at” h .“ MWHHII if 6“ or . d .o-'.“ Qouol- .‘. .. > ‘v-.o-.--..~-. , .-.- 4-. Emu—.— n—n—J-L—m- '” fldllillllllllllllllllllilllllllllIllilllIIHIIHIflIIlllHlillllll '11.! " “WI-’7 .' hf' ..- 1.r '1 In PLACE IN RETURN BOX to remove this checkout from your record. To AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 6107 p:lClRC/DateDue.indd—p.1 An Experimental Study of Materials Used in Structural Backfille By Warren William McNicol Candidate for the Degree of Bachelor of Science A Theeie submitted to the Faculty of Michigan State College of Agriculture and Applied Science July, 1943 W The author is greatly indebted to Professor C. B. Andrews of the Civil Engineering Department, Mr. GM C. Blomquist, Assistant Soils Engineer with the Michigan State Highway Department, and Professor C. L. Allen, Head of Civil Engineering Department for their guidance and suggestions in connection with the prOblem, and to the Michigan State Highway Department for the use of equipment, laboratory facilities and their kind advice, without which this work would not have been possible. 17:. v ‘u.§-.. .3. n. at! H TABLE OF CONTENTS Acknowledgment Introduction Scepe of Problem Theory Basic PrOperties of Soil Soil Tests Plan of Procedure Data Discussion of Results Conclusions BibliOgraphy 10 15 18 4O 43 45 INTRODUCTION This report is the result of study of the prime factors that influence the behavior of various materials in use today for structural backfille. Its purpose is to increase our knowledge of structural backfills which will enable engineers to design adequate support for bridge ap- proaches and culverts. Soils are the most complex of the construction mater- ials used by engineers. An engineer can readily predict how the principal building materials such as steel, concrete and brick will react in any given structure. He may predict their physical performance so clearly that the failure of a properly designed structure due to some unexpected behavior or characteristic of the material is rare. One cannot find such accurate structural data on soils and consequently de- sign and construction procedure have been largely dependent upon individual Judgment and the so called 'rule of thumb' gained from previous experience. This practice has led to an increasing number of failures of dams, tunnels, roads and other structures concerning earthwork, due to unexpected settlement, lateral flew, swelling or other performance of the soil. Soils are the results of natural processes and therefore will lack the uniformity of the common building materials. Also no sil deposit is identical to another, though they may come from areas but a few feet apart. Although design data is lacking for the structural aspect of soils, it is not due to any neglect by able re- search. Engineers and research workers have studied soils both in the field and laboratory and have developed a new science called 'Soil Mechanics'. This science considers soils as a raw material and gives consideration to its origin, past treatment, present condition and future use. However, due to their everehanging characteristics, errors from 50% to 100% are not uncommon in the deriving of soil constants. Research has acquired enough experimental data to warrant the use of soil in importantstructures. By these tried and tested methods it has been dis- covered that culvert and'bridge backfills require drain- ability to prevent the trapping of water'back of abutments and.wingwalls, and compaction tcndnimize settlements on approaches to the structure.9 A.well graded material, that is pervious to water, has been found to best satisfy these requirements. ,A material having less than 7% passing the #200 sieve will have good permeability. If clay or cohesive soils are used, which have low permeability and relatively large volume changes during wetting and.drying cycles, the wall may be forced out of shape and subject to failure by increased volume change or by increased hydrostatic pressures. With the increase in traffic, both in volume and tonnage, the interest in compaction has increased accordingly. Many contractors and engineers have not so readily accepted this fact. It is evident, on existing structures, that failures have occurred on structural backfille. The settlement and consolidation of the fill caused by impact and vibration of traffic, will no longer provide adequate support for the roadway and consequently cracking and breaking up of the road results in a deflection in the roadway that is both hazardous and adds considerably to maintenance costs. Application of these priciples, compaction and perme- ability, have been carried out in laboratory tests. future study mawaell alter some or all of the conclusions pre- sented in this report but an effort has been made to abide by careful laboratory tests and data. SCOPE OF PROBLEM .A scale model of the average'backfill, as generally found in the field, was constructed to correlate the be- havior of granular fill materials with the actual condi- tions in the field. Tests with the scale model along with some of the accepted laboratory tests give favorable data and results. The essence of the study was to determine answers to the follo'1n88 1. What compactive effort is required to 'prevent detrimental settlement in the following materials: 1 . Dune Sand 2. Natural Sand 5. Bank Run Gravel 4. Pee Gravel 5. Coarse Aggregate 6. Slag 2, What effect does water have on compaction by vibration? 3. What densities would be required when using any of these materials for structural backfills? 4. What is the best method of obtaining prOper degree of compaction? 5. What special treatment should be required when using any of the mentioned materials? The results obtained from studies of granular materials compacted by vibration and tamping with varying moisture con- .tents are summarized in this report. THEOEX; Since no actual soil is homogeneous we cannot expect to arrive at an exact understanding of their characteristics. This fact cannot be emphasized too strongly. Earth pressure and consolidation theories, of a few years ago, assumed that soils had only two recognized properties, internal friction 5 and cdhesion. The effects of moisture content, elastic pro- perties and volume change were entirely neglected.7 Today we have a better understanding of soils through Soil Mechanics. The oldest method of classifying soils is prdbably that of the distribution of grain size. The following system, used by the Bureau of Soils, U. S. Department of Agriculture, is taken as a reference: Medium gravel ’ Fine gravel 2.0 mm Coarse sand 1.0 mm Medium sand .5 mm Pine Sand .25 mm Very fine sand .1 mm Silt .05 mm Clay .0025 mm lhile a knowledge of grain distribution does not in it- self indicate the permeability or cohesion of the soil, it does give the observer some idea of the potential properties a soil may possess.4 Small voids and high cohesion, due to molecular attraction and capillary forces, normally occur in fine grained soils. Gravels and sands consist of angular or rounded grains easily seen and felt, which usually function as individual particles and result in high internal friction, very low plasticity and cohesion, good permeability and low capillary action. Clays consist of particles so small they cannot be easily seen or felt. They are highly plastic and cohesive but possess little internal friction. They are subject to marked velume changes*with.alternate wetting and drying cycles, forming large lumps when dry. Silts are of an intermediate relationship between sands and clays both.in particle size and properties. The effect of grain size has a definite effect on density. As soil particles become flatter they tend to decrease their volume of voids and obtain maximum density. A fine grained soil may be expected to have a lower density and a higher percentage of voids than one consisting of larger grains. For materials whose grains adhere to one another, due to molecular attraction, an even greater valume of voids would be expected since they would build up on top of each other and refrain from falling into void spaces. Such a structure asthis would be called I'honeycom‘bed", whereas sands would form single grained structures when the voids are about the same size as the grains.4 A typical soil is made up of air, water, solid mineral grains and probably some organic matter. The water may exist in a hydroseopie, capillary, gravitational or solidified form. . HydroscOpic water is water that surrounds the indivi- dual grains and is closely associated with them. Capillary water occurs in small voids so that the sur- face tension of the water accounts for marked behavior of a soil. Shrinkage of a soil may be considered as nothing more than compression due to a gradual increase of the capillary pressure while swelling would represent expansion resulting from reducing the capillary pressure to zero. Gravational water is water that occurs in large enough masses so as to behave according to the laws of hydraulics. The effects of the organic matter in soils are quite important, but as they occur mostly in surface soils which are not used for engineering purposes, they may be discredited here. Krynine, Terzaghi, and Plumnur agree that the trend of consoilidation depends upon the permeability of a given soil. The theory of this statement is too long to be presented in this work, but may be found in F. L. Plumnur's 'Eotee on Soil Mechanics and Foundations'; In the case of very permeable soils such as sands and gravels there is practically no consolidation process at all under a static load though some rearrangement of particles does exist.‘ However, although consOlidation does not occur in granular soils under a direct load they are much more susceptible to compaction by vibration. Moreover, the per- meability of smh soils is large enough to limit the possibili— ties of water governing the rate of settlement and therefore any settlement that takes place would do so immediately.7 Test and field conditions show that a.soil is weakest when saturated with water, since the cohesion of the particles are the least and having been lubricated slide over one another easily. It would seem that the more water that can be kept out of a soil the greater its supporting power. However, plasticity, or ability to flow, depends upon the frictional resistance of the soil particles to sliding, and in general‘the greater the amount of voids, the larger the amount of water required to:fill them and the greater the change in volume and plasticity.4’5 In order to get an embankment as little subject to change as possible it is desirable to compact the fill material to its most dense condition. If it is compacted at a low moisture content, the resulting fill may be firm and hard, but vibration or water percolating through its numerous voids would cause settle- ment. If the same soil is compacted at higher moisture con- tent the fill is firm but much more plastic. Each soil has a definite moisture content at which the density obtained will be a maximum and may be found by laboratory tests.7 It has been found that compaction of soil results in three major changes namely; 1. The decrease in tendency of soil to settle. 2. The decrease in permeability of soil. 3. The increase in supporting power.7. When structural backfills are made they must have supporting power, no further settlement and.be permeable. The problem involved is to find.the material or combination of materials that will best satisfy these prOperties. BASIQ PROPERTIE§ OF SOIL§ ZEEMEABILITX - Permeability is the susceptibility of the passage of water'through a soil and one of the most important physical characteristics. The coefficient of permeability, found by a laboratory test based on the velocities of flow, is used to determine the rate of .ssttlement of'a soil under static load. Permeability of sands and gravels are very high while clays have practically no permeability at all under certain conditions. INTERNAL FRICTION -.Internal friction is the resistance of the soil grains to sliding over one another. Silt possesses the least internal friction with gravels having . the most. The magnitude of frictional prOperties is dependent upon a number of factors, some of which are: 1. Shape of particles 2. Particle size 3. Gradation 4. Degree of consOlidation 5 e Load The angular or irregular shaped particles offer more resistance to sliding than do the smooth round particles. Large particles improve the interlocking effect of the material, while a good grading aids in a better compaction effect of individual particles. The degree of consolidation controls frictional prOperties by determining the frictional areas of the particles in contact. COHESION; - Cohesion.is the resistance of the soil grains to being separated. This prOperty is essential for stability. Clays exhibit this quality the best, and gravels have the least. A number of factors are responsible for the degree of cohesion shown by clays, among these are: 1. Percentage of clay 2. Size and shape of particles 5. Gradation 4. Moisture content CAPILLARITY - Capillarity is the ability of a soil to trans- mit moisture regardless of gravity or other ferces. Capillarity governs the rate at which a soil will absorb water, the quanity it will take, and the amount it will retain. The capillarity is directly related to grain size and grading of the material. A.compacted clay will have a high and rather slow capillary rise because of the high resistance offered‘by its small channels to water. Gravel and sands show almost no capillary rise, while silt has the most rapid and high lift of water,in many cases to such an extent as to be detrimental as construction material. SOIL TESTS; l0, 6 A number of simple soil tests hays been studied and will be found useful in connection.with compaction and drainability, however only those tests that have direct 10 «w iii Elihu ’Fit.ku.wg_ application to the problem will be discussed.here. MOISTURE COETENT - The moisture content of a soil ex- pressed as a percentage of the dry weight of the soil shall be calculated as follows: Mi: !;;_!Q, x 100 we where M = moisture content in percent. I“: weight of wet soil obtained by subtracting the weight of the containerfrom the weight of the wet soil and the container. we = weight of dry soil obtained by subtracting the weight of the container from the weight of the dry soil and container. ‘ STEVE ANALZSIS - This test is for the determination of particle size and gradation of a soil. The samples are dried to a constant weight and placed on a nest of sieves using such sieves as are necessary to determine compliance with the specifications for the mater- ial under test. The sieves are then vibrated and Jarred by a mechanical vibrator for twenty minutes. The weights of each size retained on a sieve is then determined. The results of the analysis is reported as total ;percentages passing each sieve or total percentages re- ‘tained on each sieve. SPECIFIC GRAVITIES - Dry bulk specific gravity (Go) is found by use of following: 11 where Go 3 dry bulk specific gravity we 3 weight of dry sample V 2 volume of sample found by displacement in water. This volume does not take into account the permeable voids.. Apparent specific gravity (Ga) is found by use of following: Ga : '9 Vs where Ga 3 apparent specific gravity Vs 3 volume of soil particles including permeable voids. The volume Vs is found by drying and.weighing the sample and placing it in a 500cc volumetric flask which has been filled half full with water. The flask is then rotated in the hands to remove all air in the mass. Water is then placed in flask to the 500cc mark and the weight recorded. Considering the weight or volume of the water added to flask as V, then Vs will equal (500 - V1). In case of soils with larger particles an overflow can was used to find Vs. These specific gravities are necessary to determine the percent voids present in a material and may be found 12 from the following: at Voids = 100 (1 - :2...) W This test is derived to find the percentage of voids in granular materials either in loose state or the condition of maximum density or at any given moisture content. The material is weighed and placed in a 4' dia- meter cylinder so as to fill about two—thirds of the cylinder. A 50# piston is placed on soil and twisted to get an even'bearing. The cylinder is then vibrated and a reading in inches taken of the protruding piston until the consolidation of the soil is such that read- ings are alike for a period of four minutes at which time maximum consolidation is said to have taken place. ‘laterial is then dried.and reweighed to compute the moisture content. Volumes and weights are computed so that the percent voids may be computed in the loose and consolidated state. The difference between these percent- ages is the consolidation range. Generally larger cylinders are used for coarser mater- ials than sand, for vhich a 4" cylinder is employed, how- ever as they were not availahb all tests were run in the 4' cylinder, except the coarse gravel which would.have had too great an error. 13 PROCTOR TEST FOR COMPACTLON; The Proctor test is to determine the relationship in a soil between the moisture content, dry density and theoretical maximum density. The theoretical maximum density is not the greatest density a soil may obtain, as greater densities are obtained in the natural state and by field methods of compaction. The test is regularly performed in the following manner: The sample is air dried and is passed through a screening process. In the case of sand.and gravels, the maximum specified size of coarse aggregate to eliminate coarse material. About 2500gm of the soil is selected and the water content computed. The water is added to the sample over a sufficient range to cover the optimum moisture content that produces maximum density. Enough moist soil is placed in the tamping mold (a cylinder with 4' diameter and 5' high) to:fill it a little more‘than one-third full. It is then tamped twenty-five times with a standard tamper falling through a distance of one foot. Two more layers are added and compacted in like manner. The collar of the mold is then removed and the excess soil struck off. The soil is over-dried and reweighed. Pentrometer readings are generally taken with each change in moisture for control methods in the field. 14 1. Viv , $3.4.» “K. *0. «rt. I? .5I.,C |. 23‘ I] .3“ O .3. With granular materials the pentrometer readings are not accurate and have not been used. Bands were the only materials tested in the preceding manner. A.revised.Proctor was arranged in the laboratory to accommodate the gravels. All the foregoing procedure was followed but in place of . a 4' cylinder a i cu. ft. container was used and the material was tamped 100 times for each layer. There was no gradation made on materials since compactive results as the soil exists were wanted. PLAN OF PROCEDURE A model of s.backfill was constructed with a scale of 1' = 20'. (See :13.) Tests were run with.the model in the following manner: 1. Material placed in model loose 2. Material placed in model and vibrated.with a a bullet nose vibrator. 3. Material placed in model in 4' to 6' layers and tamped with an 8' x 8' tamper that is used in the field. Moisture contents and densities were recorded on all tests and following their compaction by vibration or tamp- 1ng the fills were flooded for 20 minutes and after a reason- able length of time, the mOisture content was determined to check the drainability of the fill. 15 .VKN‘I“|~II\ JEEP—.42 Jauxoqm “.0 mkmmd. 2. 0mm: .5002 .qudm .16 Measuring Settlement of Material he... . e .. .e.§ n?‘ .. . . ..... a .2 . 4.. Cutaway View of Model After Consolidation 1'7 TABLE Type lethod Vgl.g3[ft. Vol. Dry Ileisture voids Iaterial Consolidation Orig. Final Ohangei Density percent percent 10 30 MM Loose 93.5 .2 48.7 Vibr. (17110) 100.0 .2 39.0 7 Extended 100.4 .2 30.9 Tamped(Proctor) , 105.9 11.0 M Loose 10.0 100.0 3.10 27.0 m #7 Vib. 15.0 12.0 10.2 131.7 3.10 (17110 20011 Vol.Vib.) #2 710. 131.0 3.0 (continuous vibration) 11.7 . #0 710. 11.73 10.0 14.7 144.3 4.09 10.0 (Total Vol. Extended) #4 ramped in 4710;.” 10.50 142.7 3.20 mm #1 710. 15.0 13.0 12.0 117.5 1.0 34.9 (Total Vol. 710.) 10.0 13.55 12.0 119.1 2.77 #2 MOd 11.7 in 4" layers 12.0 122.1 4.2 120.1 0.70 #3 ”.0 15.6 15.0 102.5 1.0 30.0 103.0 2.77 m M #1 710. 15.0 13.0 10.7 100.0 4.77 31 (htended) #2 Temped 4" Layers 10.8 1249? 5.4 #3 Loose 10.0 90.2 4.77 Qearse gm #1 Vibration 15.0 13.05 13.1 122.0# 1.00 (mama) #2 ramped 12.7 124.7 1.00 #2 Loose 10.0 107. 1.00 810.: #1 7101101011 10.0 13.00 13.1 90# cu/ft . 2.01 attended #2 Med 12.1 90.0# 7 7 4.99 4" Layers #3 Loose 15.0 70.1 2.0 18 e . O o . . . t a r C I I Q Q i I I s s O I 7 _ i In Pv.u.\.,rvilsIJ—an All. 5‘0“.“ 1 .1 . or.— ”I! mm Haterialx Dent Ran Gravel loieture Content in Original Sample It. Pan .74 It. Pan 0 let sample 4.32 " " 5 Dry " 4.21 .1; 3 100 '3.47 3'18; It. Do: . 425 It. 30: +- Med soil 1980 It. Boil 1555 Height of 5011 from Top of Box 5.38" '31" mg” 10.55 cu. ft. Density m 10.55 147.5 #Icu. ft. Dry Density 147.5 - (147.5 x 3.18) 1.42.7 #Iou. ft. leturated with water - no change in settlement Ioieture Content (4 hr. later) It. Pen .55 It. Pan 0 let Beagle 8.51 " " 5 Dry " 5.21 fir = 3.751 19 unl- EEIE.‘ lu'vl i ’1’ m. Isterialx lateral Send lloisture Content in Original Sample It. Pan .5 It. Pan 3 let Sample 3.24 e e . Dry e 3.10 1.002%: 5.41 It. Box 475 7 7 4’. Tamped 0011 ' 1093 It. Coil 1418 Height of 8011 from top of be: 5" 701m 3 1573.224}. 10.8 cu. ft. Density 131; 111.1 10.8 Dry Density 131.1 - (151.1 I 5.4) V 124 Saturated lith water - no change in settlement loisture Content ( 20 hr. later) It. Pan .5 It. Pan 4- 8.47 It. 7 4 3.29 2% 20 )1 . . . \ A o u. .. s _ O . . D . U . . a . . m V e e e e r e. s e ‘ V O K i 1. Wm laterialx' Pea Gravel loisture Content in Original Couple It. Pan IR. Pan 3 let Sample a e . Dry e & e 100 3 3.94 It. Box It. 30: 3 lhmped Sell It. Coil Height of soil from top of box (2.19)2 I 5 Volue 2 Density 1551 12 Dry Density 129.2 - (120.2 J .70) .20 4.23 4.2 .701 400 2031 1051 3.707 12.0 129.2 120.1 Saturated with water - no change in settlement loisture Content (20 hr. later) It. Pan It. Pan 3 let Beagle 4.2 .49 7 7 3 Dry Sample 4.00 5% x 100 g 3431 21 2mm. latex-ial: Coarse Aggregate Hoisture Content in Original Sample It. Pan .5 Wt. Pan 3 Wet Sample 4.32 It. Pan 0 Dry Sample 4.20 " 3f}:- . 100 .7: 1.001 It. Box 475 It. 00x.+ Iemped 0011 ' 2070 It. 0011 V 1000 Height of Soil from tap of box 3" Value (2,302)"3 g g 12.7 Density 13% a 126 0:7 Density 120 - (120 x 1.00) 124.7 Saturated lith later a No change in settlement Moisture Content 20 hrs. later It. Pan .5 It. Pan 3 let Sample 4.57 " " 5 917 " 4.50 All .* 100 -; 1.751 mm Iaterial: Slat Moisture Content in Original Samle Ht. Pan .67 Wt. Pan 3 Wet Soil 4.67 " " 3 Dry ' 4.48 §f%§ . 100 ; 4.991 It. Box 445 It. Box and Soil 1659 It. Soil 1214 Height of Soil from Top of Box 8.5' Volt-e (2.222 g 5 12.1 Density 1213 100.4 12.1 Dry Density 100.4 - (100.4 x 4.99) 90.5 Saturated with water - no further settlement Hoisture Content (20 hr) It. Pan .5 It. Pan 3 let Sample 4.70 77 77.017 .21 4.00 " 4.55 0.101 23 VIBRATION MATERIAL: Bank Rm Gravel Ioisture Content in Original Sample Wt. Pan .55 It. Pan 3 Hot Sample 3.67 " " 3 Dry " 3.56 . 31% . 100 :: 3.001 It. Box 425 It. Box 4- 8011 1923 It. Sci]. 1498 Height fromtop of box before vibration 4" . 3 . . aftlr n 5. Original VSlumo (2.166)2 1 § 11.73 final Vol. (33:5) 10 1 701. Settlement 2 p.10 - 19 . 100 14.71 Dry Density (Before Vibrational.” 123.2 " " (liter " ) 144.3 Saturated with water - no further settlement Hoisture content (20 hrs. later) at. pan .50 It. Pan 3: Wet Sample ‘ 5.08 " " 8 Dry Sample 4.90 all . 100 «.- - 4.131 4.35 24 I443». . .. VIBRATION Materials Natural Sand lloisture Content in Original Sample It. Pan It. Pan 3 lot Sample I a 5 Dry :7 ,1; x 100 . 2.31 It. Box It. Box 4- Soil It. S011 Height from top of box before vibration O I I 77 after I Original Vol.‘ (2.5)2 g 5 rinal,vel. (2,20§2 ; g 1 701. Settlement 1:31.50 3 13.9 x 100 Dry Density (Before Vibration) ' ' (After ' ) .75 3.17 3.00 4.772 450# 1932 1477 level 2.007. 15.0 13.0 10.71 90.2 #lcu. ft. Saturated with water - no further settlement Ioisture content (20 hrs. later) Wt. pan " 'SDrySample .11. . 100 00 25 108.6 " ' .55 3.25 .1211 2 5.52 It.) .ean "U- VIBRATION Material: Pea Gravel Moisture Content in Original Sanple It. Pan It. Pan 3 Set Sample 7 7 emyhmu .12 . 100 - 4.33 ' It. Dex Ht. Sex 5 Soil It. soil Height from top of box befu'e vibraticn I I I I after 2 I Original 701.? (2,0)2 x 5 71001 701. (2.3322 x 5 1 701. settlement (1530 - 13.50)100 15.6 Dry Density (Before Vibration) " " (After " ) .0 4.90 4.03 2.771 43031 2140 1000 Level 2. 15.0 13.50 12.02 119.1 103.0 Saturated with water - no further settlement loisture content - 28 hrs. later It. Pan Wt. Pan 3 let Sample I I . Dry I .112..0 100 4.23 26 .5 4.55 4.73 2.03% ‘ h‘n‘ir _.:r_'—.fm.—~nm~w¢. . _ VIBRATION Material: Coarse Aggregate Moisture Content in Original Sample wt. Pan ‘ .5 It. Pan 3 Wet Soil 4.32 7 7 3 Dry 7 4.20 <1°°>af%— ; 1.001 It. Box _ 47W . st, 30; 4. 3011 2147# E It. Soil 167225 5 Height from top of box before vibration level L a e s a an” a 2. Original vol. I (2,522 1 5 15.6 t...— final 701. (233)2 x 0 13.50 1 701. settlement 2 15,55 - 13.25 . 10° 13.11 Dry Density (Before Vibratiin)‘ 106.1 (After ‘ 7 ) ‘ 122.0 Saturated with water - no further settlement ° Moisture content - (20 hrs. later) Wt. Pan . .5 It. Pan 7 Net sample 4.43 e s '7 Dry sanplc 4.37 .90. . 100 = 1.01 3.87 27 a... . 17. IJI'P. VIBRATI CH Material: Slag Moisture content in original sample llt. Pen .55 It. Pan +- Hot sample 4.29 " " "' Dr: " 4.20 .19.. .‘ 10° : 2.01 3.65 It. Box 4455! .' It. box 4- soil 1695 E It. 0011 1200 ,3 Height from top of box before vibration level I I I I after I 2I h.— Original 701. (2,5)2 g 5 15.0 final 701. ' (2.33223 g 0 13.55 1 Vol. Settlement (152.6 - 13.55) 100 13.11 Dry Density (Befzore vibration) 78.1 (After " ) 90 Saturated with water - no further settlement Moisture Content - (20 hr. later) Wt. Pan .6? - 21;. Pan 2— let Sample 4.67 7 7 4 Dry " 4.48 28 I. ' l , 2 a x _ . II .7 Is 7. l4 ‘ . I . . ~ 0 \ 0 . ‘ e . . . . ..- . v ’ ‘ I g 7 ‘ ‘ . . 1 . . , , , ‘ E - 7 s ‘ ‘ . s .u. . - . ‘ _., _ I - u "l . . . \ o . ‘ ..‘ D' I 1 , . ‘- , ‘. 'I l ‘1 . ‘ I u. \ b I n l a . . I k J (J: 1 120 (Q hevlsed Proetar -—fi b-- 'O-O .4 I I) II b—— / —e-' - AI. -24.». £51,153“ lax-a 4‘“ ~ , . , . A ' mm w vim-1 .1412841.EAKB 701. 0: Cylinder It. Cylinder It. Material 1 Moisture Wt. Soil not a. Ht 011. 8011 0 5950 2.1 5900 1827 4.2 5965 1892 6.0 6014 1941 7.9 6074 2001 10.3 6111 2038 11.8 6158 2085 2m 2m 1 Moisture 0t. 0011 set -+- Wt - Cylinder Soil .4 5748 1675 3.000 5785 1712 6.2 5833 1760 8.6 5908 1835 12.2 5969 1896 11.8 5970 1897 15.1 5988 1915 P800293 DENSEE! .35 it2 4073 gm Ho 1877 1791 1816 1825 1841 1834 1735 No 1669 1662 1658 1690 1689 1697 1664 3C) Dry Density # cu/ft3 104.2 103.7 103.5 105.5 105.4 105.8 103.8 Sample -Pea Gravel 340.3 Sand Dank Bun Gravel 157.1 205 APPARENT SPECIFIC GRKVITIES WtJ‘lask Dunes}: Ht. 8 Soil 446.6 264.1 312 3 0011 3 320 020 320.2 373.0 703.1 439.0 730 423 31. Vol. Soil 3 000000010 (12141.... 120.4 61.0 77 GA 3.09 2.53 VIBROMETERERESULTS C : 6.187 P : 5.75 A : 12.56 L : X 4-0 - P V : AL 16.38 Loose Vol. I (in) Length Sample (in) Vol. of Sample wt. 01 Sample Dry It. of Sample (3m) Moisture Cont. 1 Moisture Dry. Bulk 0.0. Add. Sg. I Voids Vibfltfld Vol. I (in) Length Sample (in) v01. I Dry Bulk 8.8. Dry lt./cu. ft. 1 Voids (lensolidated Range Bank'run pea Natural gravgl stong 3.19 3.63 .3.5 3.44 3.624 4.062 3.937 3.88 744 835 808 797 1426 1459 1168 1300 1381 1387 1120 1183 45 72 48 117 3.29 5.25 4.29 9.88 1.86 1.66 1.39 1.47 2.53 3.69. 2.59 2.59 27 55 ‘ 46.5" 43.2 2.75 3.32 2.75 2.75 3.187 3.749 3.187 3.19 660 772 655 655 2.09 1.79 1.71 1.8 102 101.3 18 ‘ 51.5 34 31 9 3.5 12.5 12.2 :32 Sand 3.63 4.06 834 1325 1225 110 7.5 1.44 2.59 43.6 3.0 3.44 707 1.74 101.1 32.2 11.4 SIEVE ANALYSIS 1mm 9mm. I I 1776 31:1. Sieve no. Amt.Retained 1 05- Cumulative 21 Weight I. tamed 1 Detained. 3/4 77 4.4 4.4 1/2 73 4.1 5.5 #4 395 22.2 30.7 #10 295 15.5 47.3 500 33.7 51.0 #200 255 15.1 97.1 Pan 50 2.9 100 1512 = 1124 gm. #4 4 .5 .5 #10 52 4.7 5.2 #40 553 49.9 55.1 100 455 41.45 95.55 200 29 2.5 99.1 W 3 1046 En. 1/2 . 50 4.9 4.3 370 35.4 40.2 #10 455 43.5 53.7 107 10.3 94.0 100 50 4.5 95.5 200 7 .7 99.2 543 7 .5 100 00155: 100000170 = 2941 an. 1 ' 400 17 17 1/2 2113 55.4 55.4? 4 355 5.2 97.5 10 27 . 9 95.5 40 22 .5 99.3 100 13 .4 99.7 Pan 8 .3 100 01.10 1: 3203 cm. 14 75 2.5 2.5 1 590 21.5 24.0 1/2 1530 47.5 71.5 4 495 15.4 57.2 10 145 4.5 91.7 40 130 4.0 95.7 53 ZS _.r<.;-h.~-?.$.1v. ‘ - .:ZLQTQ 703 ' - , .. 09:} . I LOOI'O 0171 . _ i 7 _ '35:: 7 4 1’ ' 058:9; 03 , ' ' ., .' .NCW 1 ‘_- 9 . . . . fl _‘_- . 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SpouaJH annexasoa) Tests, as indicated by previous explanation of soil tests, were run on the materials with.various moisture contents to correlate and compare data with tests run on the scale model . W The preceding tables and graphs are self -explanatory and require no further clarification. Throughout the study, records were kept of the various aspects pertinent to the study of consOlidation of granular materials. The data compiled for dune sand are the results of standard or re- vised soil tests, as circumstances made it impossible to carry out tests with the scale model. The densities, volume changes and moisture contents obtained from various materials are noted in table 1. All materials showed appreciable valune change by tamping or vibration and.bence an accountable change in densities. The densities, obtained.by vibration and tamping are so near as to be considered the same in the case of dune sand and bank run gravel respectively. This aspect can be attri- buted to particle size, shape and gradation of the materials, as the major causes. Since the particles of dune sand are smooth, round and the sieve analysis shows them to be of the same general size, we can explain the situation in this manner. Nb matter how the particles are arranged when they are consolidated, they will always conform to one pattern and the vaid spaces will be the same. The particles have little internal friction 40 due to their roundness and can slide easily, hence, the compactive effort is not very great. Tamping and vibra- tion produce forces that are great enough to arrange these particles in their densest form accounting for the like densities obtained from tests. In bank run gravel the gradation is very good and there would be better imbedment of the particles. There are numerous ways in which they may arrange themselves. The small particles filling the voids between the larger par- ticles. Here again the vibration and tamping forces are great enough to arrange these particles so that the maxi- mum density, possible by mechanical means, is obtained. The small discrepancy between the densities obtained ‘by these methods of compaction for dune sand and‘bank run gravel would be the result differences between the com- pactive effort. Regardless of the method of test the higher the compactive effort, the greater the density, and the lower the Optimum moisture content. Natural sand, pea gravel and coarse aggregate show a marked difference in their ability to arrange their particles. These materials possess angular grains and therefore compaction causes an increase in the internal friction as the surface area of the grains in contact increased. Vibration of the mass can consOlidate it governed by this internal friction, 'whereas tamping produces a force that is great enough to trvercome the friction force governing compaction by vibra- tion. This causes the particles to fill a greater amount of the 41 1.343.!“ ”-444 ‘lll...l..ll.dll!flv|,llrtl!i| o