The early history of geotechnical engineering and the pioneering work of Karl Terzaghi at the turn of the last century are described in Chapter 1. Soil consolidation and the evaluation of compressibility in the laboratory through oedometer tests are explored in Chapter 7.
Th e Standar d One-Dimensiona l Consolidatio n Tes t 21 3
CHAPTERS SHEA R STRENGTH O F SOIL 25 3
Basi c Concep t o f Shearin g Resistanc e an d Shearin g Strengt h 25 3
Method s o f Determinin g Shea r Strengt h Parameters 25 5
Moh r Circl e o f Stres s When a Prismatic Elemen t i s Subjecte d t o
Othe r Method s fo r Determinin g Undraine d Shea r Strengt h
Th e Relationshi p Between Undraine d Shear Strengt h an d
Executio n o f Soi l Exploratio n Progra m 35 9
0 STABILIT Y O F SLOPES 36 5
- Genera l Consideration s an d Assumptions in th e Analysis 36 7
- Stabilit y Analysi s of Infinit e Slope s i n San d 37 1 10.5 Stabilit y Analysis of Infinit e Slope s i n Cla y 37 2
- Failur e Unde r Undraine d Condition s ((f> u = 0 ) 38 0
- Stabilit y Analysis by Metho d o f Slice s fo r Stead y Seepag e 39 3
1 LATERA L EARTH PRESSURE 41 9
2 SHALLO W FOUNDATION I
- Ultimat e Bearin g Capacit y o f Footing s Restin g o n Stratifie d
- Bearin g Capacit y o f Foundation s o n Top of a Slop e 52 9
- Cas e Histor y o f Failur e o f th e Transcona Grai n Elevato r 53 3
SHALLO W FOUNDATION II
SAFE BEARING PRESSURE AND SETTLEMENT CALCULATION 54 5
Saf e Bearin g Pressur e fro m Empirica l Equation s Based o n
Estimatio n o f Consolidatio n Settlemen t b y Usin g Oedometer
Skempton-Bjerru m Metho d o f Calculatin g Consolidatio n
SHALLO W FOUNDATION III
COMBINED FOOTINGS AND MAT FOUNDATIONS 58 5
DEE P FOUNDATION I
PART A-VERTICAL LOAD BEARING CAPACITY OF A SINGLE VERTICAL PILE 61 3
Vertica l Bearin g Capacity o f Pil e Group s Embedde d i n
Settlemen t o f Piles an d Pile Group s i n Sand s an d Gravels 68 1 15.30 Settlemen t o f Pil e Group s i n Cohesive Soil s 68 9
DEE P FOUNDATION II
BEHAVIOR OF LATERALLY LOADED VERTICAL AND
Non-dimensiona l Solution s fo r Vertical Piles Subjecte d t o
DEE P FOUNDATION III
- Advantage s and Disadvantage s o f Drilled Pie r Foundation s 74 3
- Vertica l Bearing Capacit y o f Drilled Pier s 75 4 17.8 Th e Genera l Bearin g Capacit y Equatio n fo r th e Bas e Resistanc e
FOUNDATION S ON COLLAPSIBLE AND
CONCRET E AND MECHANICALLY STABILIZED
- Condition s Unde r Whic h Rankin e an d Coulom b Formula s Ar e
- Eart h Pressur e Chart s fo r Retainin g Walls 83 6
- Desig n Consideration s fo r a Mechanically Stabilize d Eart h Wal l 85 7
- Example s o f Measure d Latera l Eart h Pressure s 87 5
SHEE T PILE WALLS AND BRACED CUTS 88 1
- Dept h o f Embedmen t o f Cantileve r Walls i n Sand y Soil s 88 5 20.5 Dept h o f Embedmen t o f Cantileve r Walls i n Cohesiv e Soil s 89 6
- Latera l Eart h Pressur e Distributio n o n Braced-Cut s 93 5 20.12 Stabilit y o f Brace d Cut s i n Saturate d Clay 93 8
SOI L IMPROVEMENT
- Introductio n
- Mechanica l Compaction
- Laborator y Test s o n Compaction
- Effec t o f Compactio n o n Engineerin g Behavio r 21.5 Fiel d Compactio n an d Contro l
- Compactio n fo r Deepe r Layer s o f Soi l 21.7 Preloadin g
- San d Compactio n Pile s an d Ston e Column s 21.9 Soi l Stabilizatio n b y th e Us e o f Admixtures
APPENDIX A S I UNITS IN GEOTECHNICAL ENGINEERING 987 APPENDIX B SLOP E STABILITY CHART S AND TABLES 993
INTRODUCTION
GENERA L REMARK S
Because of the continued efforts of these and countless other researchers, soil mechanics and foundations have remained a very important part of the civil engineering profession. This process consists of proper observation sufficiently early during construction to detect signs of deviation of actual conditions from those assumed by the designer and to change either the design or the method of construction accordingly. e with findings.
A BRIE F HISTORICA L DEVELOPMEN T
However, in today's scientific age, foundation design based on scientific analysis has received a major boost. Darcy (1856), based on his experiments on filter sand, proposed a law for the flow of water in permeable materials, and in the same year Stokes (1856) gave an equation for determining the terminal velocity of solid particles falling into liquids.
SOI L MECHANIC S AN D FOUNDATIO N ENGINEERIN G
One of the most important contributions to engineering science was made by Boussinesq (1885), who proposed a theory for determining the stress distribution under a loaded zone in a semi-infinite, elastic, homogeneous and isotropic medium. Felleniu s (1927) led a Swedish geotechnical commission to determine the causes of failure of many railway and canal embankments.
SOIL FORMATION AND CHARACTERIZATION
- INTRODUCTIO N
- ROC K CLASSIFICATIO N
- FORMATIO N O F SOILS
- GENERA L TYPES OF SOILS
- COMPOSITIO N O F CLAY MINERAL S
- STRUCTUR E O F CLAY MINERAL S
- CLA Y PARTICLE-WATE R RELATIONS
- SOI L MASS STRUCTURE
Some of the important rocks belonging to the igneous group are granite and basalt. In the actual formation of the sheet silicate minerals, the phenomenon of isomorphic substitution occurs frequently.
SOIL PHASE RELATIONSHIPS, INDEX PROPERTIES AND CLASSIFICATION
SOI L PHAS E RELATIONSHIP S
MASS-VOLUM E RELATIONSHIP S
The water content, w, in the soil mass is defined as the ratio between the mass of water, Mw, in voids and the mass of solids, Ms, as. The specific gravity of a substance is defined as the ratio between its mass in air and the mass of an equal volume of water at a reference temperature of 4 °C.
For S < 100%
For S= 100%
For S = 0%
When the soil is submerged
- WEIGHT-VOLUM E RELATIONSHIP S
- COMMENT S O N SOIL PHAS E RELATIONSHIP S
- INDE X PROPERTIE S OF SOILS
- TH E SHAP E AN D SIZ E O F PARTICLES
- SIEV E ANALYSI S
- TH E HYDROMETER METHO D OF ANALYSIS
- GRAI N SIZ E DISTRIBUTIO N CURVE S
- RELATIV E DENSITY O F COHESIONLESS SOILS
- CONSISTENC Y O F CLAY SOIL
- DETERMINATIO N O F ATTERBERG LIMIT S Liquid Limi t
- DISCUSSIO N ON LIMITS AN D INDICES
- PLASTICIT Y CHAR T
- GENERA L CONSIDERATION S FO R CLASSIFICATION O F SOILS It has been stated earlier that soil can be described a s gravel, sand, silt and clay according to grain
- FIEL D IDENTIFICATIO N O F SOILS
- CLASSIFICATIO N O F SOIL S
- TEXTURA L SOI L CLASSIFICATIO N U.S. Departmen t of Agriculture System (USDA)
- AASHT O SOI L CLASSIFICATIO N SYSTE M
- UNIFIE D SOI L CLASSIFICATION SYSTEM (USCS)
- COMMENT S O N THE SYSTEMS O F SOIL CLASSIFICATIO N The various classificatio n system s described earlie r are based on
- PROBLEM S
Soil Phase Relationships, Index Properties and Soil Classification 4 1 related to the specific gravity of the suspension. Read for obtaining percent fine r. The 15 2 H hydrometer is calibrated for a suspension with a specific gravity of solids Gs = 2.65. The nature of the land can be assessed by determining its liquidity index, /; from cf.
Determine (a) the natural water content, (b) the in situ void ratio, (c) the degree of saturation, and (d) the saturated unit weight of the soil. 2 Water content % Number of blows, N. Plasticity limit of sample no. 1 is 40 percent, sample no. i).
SOIL PERMEABILITY AND SEEPAGE
SOI L PERMEABILIT Y
As the water flows from A to B, there is a loss of energy which is represented by the difference in total heads H, a d HD. where, pA an d pB = pressure heads, VA and VB = velocity, g - acceleration n due to gravity, yw = unit weight of water, h = head loss. The head loss of h units occurs when water flows from A to B. The head loss per unit length of flow can be expressed as a s. where / is called the hydraulic gradient. Problems relating to the flow of liquids may generally be divided into two main classes: 1. Those in which the flow is laminar.
DARCY' S LAW
The main difference between laminar flow and turbulent flow is that in the former case the velocity is proportional to the first power of the hydraulic gradient, /, whereas in the latter case it is 4/7 the power of . 4.4) is the cross-sectional area of the soil perpendicular to the flow direction, which includes the area of the solids and voids, whereas the area a in Eq. 4.3) is that the flow through the soil is also proportional to the first power of the hydraulic gradient i as stated by Poiseuille's law. From this we are justified in concluding that the flow of water through the pores of a soil is laminar.
DISCHARG E AN D SEEPAG E VELOCITIES
I t i is inverse y proportional to the viscosity y of water r which h decreases with increasing temperature as shown in Fig. If the soil is represented a s divided into solid matter and empty space, then the surface available for the passage of water r is only y Av. If vs is the velocity y of voids flo w i n , an d v , the average velocity across the section then, we have.
METHOD S O F DETERMINATION O F HYDRAULI C CONDUCTIVITY O F SOILS
The results of tests on such reconstructed soils are often misleading, as it is impractical to obtain representative samples and place them in the test equipment to obtain the exact same density and structural arrangement of particles. Direct testing of the soil present is generally preferred in cases where it is not possible to obtain undisturbed samples.
CONSTAN T HEA D PERMEABILITY TEST
As this method is quite expensive, it is generally carried out in connection with large projects such as foundation investigations for dams and large bridges or construction of foundation works where lowering of the water table is involved. One of the most important of these results from the formation of a filter sheet of fine material on the surface of the sample. In this apparatus the head loss is measured over a distance inside the sample, and the drop in head across the filter sheet has no effect on the results.
FALLIN G HEA D PERMEABILIT Y TES T
The constant head permeameter test is more suitable for coarse-grained soils such as gravelly sands and coarse to medium sands. If the time is too long, evaporation of water from the water surface may occur and also temperature changes may affect the sample volume. For such lands, the cross-section of the center tube is made with the same cylinder in order to measure the head.
According to Darcy's law, the rate of inflow into the well is when the water levels in the wells remain stationary. The equation for k after integration and rearrangement is. 4.17), where DQ is the depth of maximum drawdown in the test well, we have. 4.19) Radius of Influence R^ Based on experience, Sichard t (1930) gave an equation for estimating the radius of influence for the stabilized flow condition as. The water level in the test well can remain above the roof level of the aquifer in a constant flow condition.
The wate r level in the test well might remain above the roof leve l o f the aquifer at steady flo w condition
4.17), where DQ is the depth of maximum drawdown in the test well, we have. 4.19) Radius of Influence R^ Based on experience, Sichard t (1930) gave an equation for estimating the radius of influence for the stabilized flow condition as. The water in the observation well s rises above the top of the aquifer due to artesian pressure. The water level in the test well may drop below the roof level of the aquifer at a constant flow condition.
The water level in the test well might fall below the roof leve l of the aquifer at steady flow condition
- BOREHOL E PERMEABILIT Y TEST S
- APPROXIMAT E VALUE S O F THE HYDRAULI C CONDUCTIVIT Y OF SOIL S
- EMPIRICA L CORRELATION S FOR HYDRAULIC CONDUCTIVIT Y Granular Soil s
- HYDRAULI C CONDUCTIVITY O F ROCKS B Y PACKER METHO D Packers ar e primaril y used i n bore hole s fo r testin g th e permeabilit y o f rock s unde r applie d
- SEEPAG E
- LAPLAC E EQUATIO N
- FLO W NE T CONSTRUCTIO N
- DETERMINATIO N O F QUANTITY O F SEEPAG E
- DETERMINATIO N O F SEEPAGE PRESSUR E
- DETERMINATIO N O F UPLIFT PRESSURE S
- SEEPAG E FLOW THROUGH HOMOGENEOU S EART H DAMS
- FLO W NET CONSISTING O F CONJUGATE CONFOCAL PARABOLAS As a prelude to the study of an ideal flow net comprising of parabolas a s flow and equipotential
- PIPIN G FAILUR E
- PROBLEM S
Y found that the effective grain size of D5 would be a better choice compared to D}Q. The sand used in the investigation had a uniformity coefficient of These requirements were developed based on the Terzaghi tests, which were later expanded by the United States. The resulting filter specifications relate the protection filter classification to that for earth protected by the following:. a) The size of the smallest spherical particle that just fits into the space between the large r spheres of the Soil into which it has migrated. filter and is retained by D85 size soil particles. Confocal parabolas can be constructed with the focus of the parabola at t A. The base parabola a passes through h point G such that.
Substituting for aQ in Eq. b), the coordinates of a number of points on the basic parabola can be calculated. The amount of seepage over section Az can also be calculated without the flight net using Eq. Let RS be the equipotential line passing through P. The number of equipotential drops up to the point P is equal to 2.4.
EFFECTIVE STRESS AND PORE WATER PRESSURE
INTRODUCTIO N
The expulsion of water from the pores lowers the pore water pressure and increases the intergranular pressure accordingly. The pore water pressure uw can be induced in the pores of a soil mass by a head of water over it. The pore water pressure uw must always be less than the pore air pressure (ua).
STRESSE S WHE N N O FLO W TAKE S PLAC E THROUGH THE SATURATED SOI L MAS S
When no water flows through the pores of the mass, the intergranular pressure remains constant at one level. In partially saturated soil, part of the void space is occupied by water and part by air.
STRESSE S WHEN FLO W TAKE S PLAC E THROUGH TH E SOI L FROM TO P TO BOTTO M
Equation (5.13) shows that hzYjz{ i is the increase in effective pressure e as water flows from the surface to a depth z. It can be noted that h is the total head loss when water flows from the top surface of the sample at a depth zr. Sinc e (/z/Zj ) = /, the hydraulic gradient, the head loss at depth z can be expressed as iz.
This increase in effective pressure due to the flow of water through soil pores is known as seepage pressure. At any depth z, zyb i is the submerged earth pressure acting downward and izyb is the drainage pressure acting upward. The critical gradient of natural granular soil deposits can be calculated if the void ratios of the deposits are known.
EFFECTIV E PRESSURE DUE TO CAPILLAR Y WATER RIS E IN SOIL The term wate r level, wate r table an d phreatic surfac e designate th e locus o f the levels to which
What is the effective vertical pressure at a depth of 37 ft below the top of the shale. What is the depth of the water table outside the excavation below the original ground level. This point lies in the clay layer at a depth of 1 m below the bottom of the clay layer.
PROBLEM S
Calculate the pore pressure and effective stresses at elevation A when (a) the water table is at elevation A, and (b) when the water table rises to El.B. 5.6, determine the effective loads at point A for the following conditions: (a) water table at ground level, (b) water table at El.A. assume that the soil above this level remains saturated), and (c) the water table 6.5 feet above the ground surface.
STRESS DISTRIBUTION IN SOILS DUE TO SURFACE LOADS
- INTRODUCTIO N
- BOUSSINESCT S FORMUL A FO R POINT LOAD S
- WESTERGAARD' S FORMUL A FO R POINT LOAD S
- LIN E LOAD S
- STRI P LOAD S
- STRESSE S BENEAT H THE CORNE R O F A RECTANGULAR FOUNDATION
The expression obtained d by Boussinesq for calculating the vertical stress <7 , at point P (Fig. 6.1 ) due to a load point Q is. The strain rate in the XZ plane (Fig. 6.3) is the same in all sections and the shear stresses in these sections are zero. Applying the theory of elasticity, the stress is a point y t P (Fig .. 6.3 ) can be obtained d or polar coordinates r i n or rectangular coordinates r.
