BASIC SOIL MECHANICS

Prof.(Dr.) SUDHENDU SAHA

Chartered Professional Engineer

Civil Structural Geotechnical Consultant

Formerly

Professor and Head of The Dept. of Civil Engineering,

DEAN of Research Consultancy & Industry Institute Interaction,

Bengal Engineering and Science University, Sibpur

 

SOIL IS A COMPLEX MIXTURESOIL IS A COMPLEX MIXTURE

OF OF

PARTICLES OF DIFFERENT SIZESPARTICLES OF DIFFERENT SIZES

DIFFERENT ORIGINDIFFERENT ORIGIN

DIFFERENT MINERALSDIFFERENT MINERALS

DIFFERENT PROCESS OF FORMATIONDIFFERENT PROCESS OF FORMATION

DIFFERENT STRESS HISTORYDIFFERENT STRESS HISTORY

SOIL AS THREE PHASE SYSTEM

VOID RATIO ,

MOISTURE CONTENT,

DENSITY

PARTICLE SIZE DISTRIBUTIONPARTICLE SIZE DISTRIBUTION

UNIFORMITY COEEFICIENT

EFFECTIVE SIZE

COEFFICIENT OF CURVATURE

% OF SAND SILT & CLAY

Soil Classification Soil Classification based on particle sizes :based on particle sizes :

  

Boulder over 300 mmBoulder over 300 mmCobble 80 to 300Cobble 80 to 300

Gravel 4.75 to 80Gravel 4.75 to 80 C Coarse Sand 2.00 to 4.75oarse Sand 2.00 to 4.75 Medium Sand 0.425 to 2.00Medium Sand 0.425 to 2.00 Fine Sand 0.075 to 0.425Fine Sand 0.075 to 0.425 Silt 0.075 to 0.002Silt 0.075 to 0.002

Clays < 0.002 mmClays < 0.002 mm

Soil Classification according to Plasticity Index of clayey soils :

Plasticity Index Classified as

0 Non-Plastic < 7 Low Plastic 7 – 17 Medium Plastic

> 17 Highly Plastic

when, Plasicity Index = Liquid Limit – Plastic Limit

BROAD CLASSIFICATION OF SOILSBROAD CLASSIFICATION OF SOILS

COARSE GRAINED SOILSCOARSE GRAINED SOILSGW, GP, GM, GCGW, GP, GM, GCSW, SP, SM, SCSW, SP, SM, SC

FINE GRAINED SOILSFINE GRAINED SOILSML, CL, OLML, CL, OLMI, CI, OIMI, CI, OI

CH, OH, PtCH, OH, Pt

SOIL INVESTIGATIONSOIL INVESTIGATION

PLANNING SOIL INVESTIGATION PROGRAMME

DEPTH & NUMBER OF BORE HOLES

BORING & SAMPLING

FIELD TESTS OF SOILS

STANDARD PENETRATIUON TESTS

VANE SHEAR TEST

PLATE LOAD TEST

PLANNING SOIL EXPLORATION PROGRAM

DEPTH OF BORE HOLES

STANDARD PENETRATION STANDARD PENETRATION TESTTEST

N-Value vs Angle of Internal Friction of Soil

STATIC CONE STATIC CONE PENETRATION TESTPENETRATION TEST

Angle of Internal Friction of Soil

Static Cone Resistance

VS

Angle of Internal Friction Of Soils

LABORATORY TESTS OF SOILSLABORATORY TESTS OF SOILS

PARTICLE SIZE DISTRIBUTIONPARTICLE SIZE DISTRIBUTIONTRIAXIAL SHEAR TESTSTRIAXIAL SHEAR TESTS

CONSOLIDATION TESTCONSOLIDATION TESTSPECIFIC GRAVITY OF SOILSSPECIFIC GRAVITY OF SOILS

ATTERBERG’S LIMITSATTERBERG’S LIMITS

PROCTOR’S COMPACTION PROCTOR’S COMPACTION TESTTEST

TRIAXIAL SHEAR TESTSTRIAXIAL SHEAR TESTS

TYPICAL MOHR-COULOMB FAILURE CURVE

COULOMB’S EQUATION

S = C + ( - u) tanFAILURE CRITERIA

SRELATIONSHIP OF PRICIPAL STRESSES AND

SHEAR PARAMETERS

1 = 3 tan2 (450 + / 2 ) + 2C tan (450 + /2)

TYPICAL COMPACTION CURVESTYPICAL COMPACTION CURVES

COMPACTION CHARACTERISTICS OF FINE

GRAINED SOILS

COMPACTION CURVE FOR SANDS

DETERMINATION OF STRESSES

AT DIFFRRENT DEPTHS BELOW FOUNDATION LEVEL

CONTACT PRESSURE DISTRIBUTION BELOW FOUNDATION

DETERMINATION OF VERTICAL STRESS AT ANY DEPTH BELOW

UNIFORMLY LOADED RECTANGULAR AREA

VERTICAL STRESS AT ANY POINT BELOW UNIFORMLY LOADED

CIRCULAR AREA

NEWMARK CHART

DETERMINATION OF STRESSES AT DIFFERENT DEPTHS BELOW

FOUNDATION AREA OF ANY SHAPE

IMMEDIATE SETTLEMENT

4

21)( I

EqbaverageSe

CONSOLIDATION SETTLEMENT

Sc = . h . mv . p

0

0

0

ln1 p

ppC

e

hS cc

MODES OF SHEAR FAILURE BELOW FOOTING

ENGINEERING APPRECIATION

PERFORMANCE CRITERIA

EFFECTS OF TOTAL AND DIFFERENTIAL SETTLEMENTS

SEISMIC RESPONSE OF SOILS

(a) In Seismic Coefficient Method : h = . I .0

(b) In response Spectrum Method : h = . I. F0 Sa /g

HORIZONTAL SEISMIC COEFFICIENT

SHEAR WAVE VELOCITY

LIQUEFACTION

FACTOR OF SAFETY AGAINST LIQUEFACTION

F.S. = CRR / CSR

SEISMIC EFFECTS ON STRUCTURES WITH UNEVEN LOADS

DESIGN OF SHALLOW FOUNDATIONS

LOCATING NEW FOUNDATION NEAR EXISTING FOUNDATION

EFFECT OF STRESS FROM ONE FOUNDATION TO ANOTHER

SPECIAL FOUNDATIONS

TYPICAL FOUNDATIONS

FOR

OIL STORAGE TANKS

REINFORCED EARTH FOUNDATIONS

GEOSYNTHETICS

APPLICATIONS

REINFORCEMENTS

SEPARATION

EROSION CONTROL

FILTRATION

DRAINAGE

TRANSMISSION

IMPROVEMENT OF BEARING CAPACITY

INTERACTION OF REINFORCEMENT WITH FAILURE WEDGES

MODES OF FAILURE

SHEAR FAILURE OF SOIL AGAINST REINFORCEMENT

REINFORCEMENT PULLOUT FAILURE

REINFORCEMENT TENSION FAILURE

TYPICAL SECTION OF A REINFORCED EARTH

RETAINING WALL

TYPICAL SECTION OF A REINFORCED EARTH BRIDGE

ABUTMENT

DESIGN OF

MACHINE FOUNDATIONS

MODES OF VIBRATION

DESIGN CRITERIA

THEORY OF VIBRATION

DYNAMIC PROPERTIES OF SOILS

VIBRATION ISOLATION

GROUND IMPROVEMENT METHODS

COMPACTION

DENSIFICATION

STABILISATION

GROUTING

USE OF GEOSYNTHETICS

PRELOADING WITH VERTICAL DRAINS

IMPROVEMENT OF SOFT CLAY SOILS

USE OF VERTICAL DRAINS

FOLLOWED BY

VERTICAL DRAINS LIKE

1. SAND DRAINS

2. SAND WICKS

3. PREFABRICATED DRAINS

4. STONE COLUMNS

THEORETICAL CONSIDERATIONS

U% = f(T)

Ur = Cvr.t / de2

Uv = Cv.t / de2

U = 1 - ( 1- Ur) (1-Uv)

TIME FACTOR

VS

DEGREE OF CONSOLIDATION

DESIGN AND CONSTRUCTION OF

STONE COLUMNS

LOAD TRANSFER MECHANISM IN PILE AND

STONE COLUMN

LOAD BEARING CAPACITY

OF STONE COLUMN

NCK

qZK

dP su .421

34

.00

2

LOAD BEARING CAPACITY OF TREATED GROUND

A

PqAAq safespsafe

SETTLEMENT ANALYSIS OF GROUND TREATED WITH

STONE COLUMNS

PILE FOUNDATIONS

RANGE OF APPLICATIONS

TYPES OF PILES

CONSTRUCTION METHODS

EFFECTS OF INSTALLATION

NEGATIVE SKIN FRICTION

LOAD BEARING CAPACITY OF PILES

ULTIMATE LOAD CAPACITY

Qu = Qp + Qf

Qp = Ap {Nc Cp + Pd Nq + 0.5 d N}

Qf = d { C l + K l Pz tan }

BEARING CAPACITY FACTOR N9

PILE GROUP CAPACITY

PILE GROUP MAY AFFECT THE SOIL STRATA AT DEPTH

INTERACTION BETWEEN PILES IN A GROUP