Introduction to Soil Mechanics E-Book

Béla Bodó

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 430

Veröffentlichungsjahr: 2013

Beschreibung

INTRODUCTION TO SOIL MECHANICS

Introduction to Soil Mechanics covers the basic principles of soil mechanics, illustrating why the properties of soil are important, the techniques used to understand and characterise soil behaviour and how that knowledge is then applied in construction. The authors have endeavoured to define and discuss the principles and concepts concisely, providing clear, detailed explanations, and a wellillustrated text with diagrams, charts, graphs and tables. With many practical, worked examples and end-of-chapter problems (with fully worked solutions available at www.wiley.com/go/bodo/soilmechanics) and coverage of Eurocode 7, Introduction to Soil Mechanics will be an ideal starting point for the study of soil mechanics and geotechnical engineering.

This book’s companion website is at
www.wiley.com/go/bodo/soilmechanics and offers invaluable resources for both students and lecturers:

• Supplementary problems
• Solutions to supplementary problems

Leseprobe

Contents

Preface

List of Symbols

Chapter 1: Soil Structure

1.1 Volume relationships

1.2 Weight–volume relations

1.3 Alteration of soil structure by compaction

1.4 California bearing ratio (CBR) test

1.5 The pycnometer

Supplementary problems for Chapter 1

Chapter 2: Classification of Cohesive Soils

2.1 Atterberg Limits

2.2 Consistency indices

2.3 Classification of soils by particle size

Supplementary problems for Chapter 2

Chapter 3: Permeability and Seepage

3.1 Coefficient of permeability (k)

3.2 Seepage velocity (υS)

3.3 Determination of the value of k

3.4 Field pumping tests

3.5 Permeability of stratified soil

3.6 Flow nets

3.7 Erosion due to seepage

3.8 Prevention of piping

3.9 Flow net for earth dams

Supplementary problems for Chapter 3

Chapter 4: Pressure at Depth Due to Surface Loading

4.1 Concentrated point load

4.2 Concentrated line load

4.3 Uniform strip loading (Michell’s solution)

4.4 Bulb of pressure diagrams

4.5 Vertical pressure under triangular strip load

4.6 Vertical pressure under circular area

4.7 Rectangular footing

4.8 Footings of irregular shape

4.9 Pressure distribution under footings

4.10 Linear dispersion of pressure

Supplementary problems for Chapter 4

Chapter 5: Effective Pressure (σ′)

5.1 Unloaded state

5.2 Loaded state

5.3 Flooded state

5.4 Types of problem

5.5 Effect of seepage on shallow footings

5.6 Ground water lowering (at atmospheric pressure)

5.7 Reduction of artesian pressure

5.8 Capillary movement of water

Supplementary problems for Chapter 5

Chapter 6: Shear Strength of Soils

6.1 Coulomb-Mohr Theory

6.2 Stress path (Lambe, 1964)

6.3 Effect of saturation

6.4 Measurement of shear strength

6.5 Thixotropy of clay

6.6 Undrained cohesion and overburden pressure

Supplementary problems for Chapter 6

Chapter 7: Consolidation and Settlement

7.1 Consolidation

7.2 The pressure-voids ratio curve

7.3 Forms of the σ′ –e curve

7.4 Coefficient of compressibility (av)

7.5 Coefficient of volume change (mv)

7.6 Estimation of settlement

7.7 Rate of consolidation

7.8 Pore pressure isochrones

7.9 Coefficient of permeability (k)

7.10 Time from similarity

7.11 Total settlement

Supplementary problems for Chapter 7

Chapter 8: Lateral Earth Pressure

8.1 Resistance to active expansion

8.2 The value of K0

8.3 Stress path representation (Lambe 1967)

8.4 Rankine’s theory of cohesionless soil

8.5 Rankine–Bell theory for c – ϕ soil

8.6 Rankine–Bell theory for c-soil

8.7 Pressure–force and its line of action

8.8 Wall supporting sloping surface

8.9 General formulae for c – ϕ soil

8.11 Height of unsupported clay

8.12 Wedge theories

8.13 Stability of retaining walls

8.14 Sheet piles

8.15 Anchored sheet pile walls

8.16 Effect of ground water

8.17 Stability of deep trenches

8.18 Bentonite slurry support

Supplementary problems for Chapter 8

Chapter 9: Bearing Capacity of Soils

9.1 Terminology

9.2 Shallow strip footing

9.3 Influence of footing shape

9.4 Shallow rectangular footing

9.5 Deep foundations

9.6 Standard penetration test (SPT)

9.7 Pile foundations (z/B>5)

9.8 Some reasons for choosing piles

9.9 Some reasons for not choosing piles

9.10 Effects necessitating caution

9.11 Negative skin friction

9.12 Stress distribution around piles

9.13 Load-carrying capacity of piles

9.14 End bearing resistance and SPT

9.15 Influence of pile section on Qu

9.16 Group of piles

Supplementary problems for Chapter 9

Chapter 10: Stability of Slopes

10.1 Short-term and long-term stability

10.2 Total stress analysis (cohesive soils)

10.3 Effective stress analysis (cohesive soils)

10.4 Stability of infinite slopes

Supplementary problems for Chapter 10

Chapter 11: Eurocode 7

11.1 Introduction

11.2 Recommended units

11.3 Limit states

11.4 Design procedures

11.5 Verification procedures

11.6 Application of partial factors

Appendix A: Mass and Weight

Appendix B: Units, Conversion Factors and Unity Brackets

Appendix C: Simpson’s Rule

Appendix D: Resultant Force and Its Eccentricity

Appendix E: References

Index

About the companion website

This book’s companion website is at www.wiley.com/go/bodo/soilmechanics and offers ­invaluable resources for students and lecturers:

Supplementary problems Solutions to supplementary problems

www.wiley.com/go/bodo/soilmechanics

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Library of Congress Cataloging-in-Publication Data

Bodo, Bela, (Engineer)Introduction to soil mechanics / Bela Bodo, Colin Jones.pages cmIncludes bibliographical references and index.

ISBN 978-0-470-65943-4 (pbk. : alk. paper) – ISBN 978-1-118-55387-9 (emobi) –ISBN 978-1-118-55388-6 (epub) – ISBN 978-1-118-55389-3 (epdf) 1. Soil mechanics. I. Title.TA710.B617 2013624.1′5136–dc23

2012040913

A catalogue record for this book is available from the British Library.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.

Cover image courtesy of Shuttlestock.comCover design by Steve Thompson

Preface

This book is intended to introduce the subject to students studying for BTEC Higher National Certificate/Diploma in Civil Engineering and Building Studies or for a Degree in Civil Engineering. It should also be practical reference to Architects, Geologists, Structural and Geotechnical Technicians.

The primary aim is to provide a clear understanding of the basic concepts of Soil Mechanics. We endeavoured to avoid the temptation of over-elaboration by providing excessively detailed text, unnecessary at this early stage of technical studies.

The purpose of this publication is threefold:

1. To introduce the student to the basics of soil mechanics.

2. To facilitate further advanced study.

3. To provide reference Information.

In order to satisfy the above requirements, the concepts of the subject are defined concisely, aided by diagrams, charts, graphs, tables and worked examples as necessary.

The text may appear to be excessively analytical at first sight, but all formulas are derived in terms of basic mathematics, except for a few requiring complicated theory, for those interested in working from first principles. They can be applied however, without reference to the derivation. The expressions are numbered and referred to throughout the text.

There are numerous worked examples on each topic as well as supplementary problems. All examples and problems are solved, many of them interrelated so that solutions can be compared and verified by means of several methods.

Some soil testing procedures are outlined only, as there are a number of excellent, detailed, specialized books and laboratory manuals available to cover this part of the subject.

There is some emphasis on the units employed and on the difference between mass and weight. This subject is discussed in Appendix A.

Béla Bodó and Colin Jones

Dedication

“I dedicate this book to my late wife Dorie.”

                                                     Béla Bodó

Acknowledgments

We wish to express our appreciation to Mr. Norman Seward, Senior Lecturer in Civil Engineering at the University of Wales College, Newport for his technical advice as to the presentation of the subject.

We are also grateful to Mr. Gregory Williams for his help in the production of this book.

We would like to thank ELE International for their support in providing product images.

List of Symbols

Chapter 1

CBR

California bearing ratio

Cr

Relative compaction

Dr

Relative Density

e

Voids ratio

Gs

Specific gravity

k

CBR Load-ring factor

M

Total Mass of sample

m

Moisture (water) content

mo

Optimum moisture content

Ms

Mass of solids

Mw

Mass of water

n

Porosity

P

CBR applied force

Pa

Percentage of air voids

Q

CBR Load gauge reading

Sr

Degree of saturation

V

Total volume of sample

Va

Volume of air

Vc

Volume of calibrating cylinder

Vs

Volume of solids

Vv

Volume of voids

Vw

Volume of water

W

Total weight of sample

Ws

Weight of solids

Ww

Weight of water

δ

CBR Penetration distance (delta)

γ

Bulk weight density (Gamma)

γ′

Submerged weight density

γd

Dry Weight density

γd

Dry Unit weight to be achieved by compaction

γs

Weight density of solids

γsat

Saturated weight density

ρ

Bulk mass density

ρd

Dry mass density

ρsat

Saturated mass density

ρ′

Submerged mass density

ρs

Mass density of solids

Chapter 2

Cd

Correction for dispersing agent

Cm

Meniscus correction

D

Equivalent particle diameter

D10

Effective size of a particle

f

Specific Volume change

H

Height from the top of the bulb to surface

hb

Length of bulb

HR

Height of centre of bulb to surface

LI

Liquidity index

LL

Liquid limit

Mp

Mass passing the nth sieve

Mr

Mass retained on the nth sieve

mT

Temperature correction

N

Number of blows

PI

Plasticity index

PL

Plastic limit

Pn

Percentage of soil passing the nth sieve

R

Mixing ratio

R′h

Recorded hydrometer reading

Rh

Corrected hydrometer reading

RI

Relative consistence index

SL

Shrinkage limit

T

Temperature

t

Time

U

Uniformity coefficient

u

Velocity of sedimentation

Vb

Volume of hydrometer bulb

Vo

Volume of over-dried specimen

≈

Volume at SL

x

Magnitude of linear shrinkage or swelling

Z

Saturation limit

η

Dynamic viscosity <eta>

Chapter 3

A

Cross-sectional area of specimen

a

Cross-sectional area of standpipe

As

Cross-sectional area of solids in specimen

Av

Cross-sectional area of voids in specimen

EPL

Equipotential line

FL

Flow Line

Fs

Factor of safety

GL

Ground level

GWL

Groundwater level (Water Table)

h

Head loss

HT

Total head at x

Hx

Head loss to point x

hx

Pressure head at x

i

Hydraulic gradient

iav

Average hydraulic gradient

ic

Critical hydraulic gradient

ie

Exit gradient

k

Coefficient of permeability

L

Length of flow path

Ne

Number of squares (head drops)

Nf

Number of flow channels

Nx

Number of head drops to point x

P

Hydrostatic force

Q

Flowrate

q

Quantity of flow in time (t)

R

Radius of influence

r

Radius to observation well

ro

Radius of central well

S

Seepage force

ux

Seepage pore pressure at x

Δh

Head Loss between equipotential line

υ

Discharge velocity

υs

Seepage velocity

Chapter 4

I

Influence factor

n

Number of elements on the Newmark chart

Q

Concentrated point load

q

Uniformly distributed load (UDL)

r

Radius

z

Depth

σ

Horizontal pressure

σv

Vertical pressure

τ

Shear stress

Chapter 5

dh

Total deformation of specimen of thickness h

hA

Artesian pressure head

hc

Capillary head

hs

Seepage pressure head

ic

Critical hydraulic gradient

mE

Equilibrium moisture content

mo

Optimum moisture content

pF

Soil suction index

PI

Plasticity index

Sr

Degree of saturation

Ss

Soil suction

T

Surface tension

u

Pore pressure

ucs

Pore pressure in the capillary fringe

uh

Static pore pressure at depth h

us

Seepage pore pressure

zc

Critical depth for piping

Δu

Small change in u

Δγ

Change in unit weight

Δσ

Small change in σ

Δσ ′

Small change in σ ′

δ

Deformation of specimen at time t

σ

Total pressure

σ ′

Effective pressure

σA

Artesian pressure

Chapter 6

A

Pore pressure coefficient

Pore pressure coefficient

B

Pore pressure coefficient

c

Cohesion

cu

Undrained shear strength

CD

Consolidated-drained test

CU

Consolidated-undrained test

ESP

Effective stress path

NCC

Normally consolidated clay

n

Proving ring constant

OCC

Over consolidated clay

p&q

Stress path coordinates

pf&qf

Stress path coordinates at failure

QU

Quick-undrained test

rx

Force dial reading at x

TSP

Total stress path

UU

Unconsolidated-undrained test

x

Strain gauge reading

Δud

Change in pore pressure due to Δσd

Δuc

Change in pore pressure due to Δσc

Δσc

Change in cell pressure

Δσd

Change in the deviator stress

ε

Strain at x

φ

Angle of friction

σn

Normal pressure

σx

Deviator stress at x

σu

Unconfined compression strength

τ

Shear stress

τf

Shear stress at failure

τp

Shear stress on a plain

τm

Maximum shear stress

Chapter 7

Ac

Area indicating completed consolidation

At

Area under an isochrone

av

Coefficient of compressibility

Cα

Coefficient of Secondary settlement () to consolidation

Cc

Compression index

Cv

Coefficient of consolidation

Dx

Dial reading at stage x

dHi

Initial settlement

E

Modulus of elasticity

e0

Initial voids ratio

ef

Final voids ratio

es

Voids ratio after swelling

ex

Voids ratio at stage x

H

Layer thickness

H0

Flow path

hx

Height of specimen at stage x

Ip

Influence factor

k

Coefficient of permeability

mv

Coefficient of volume change

OCR

Overconsolidation ratio

q

Bearing pressure

Tv

Time factor

t

Time

U

Average degree of consolidation

Uz

Degree of consolidation

u

Pore pressure at time t

u0

Initial pore pressure

ΔH

Long-term consolidation settlement

Δσ′

Effective consolidating pressure

δ

Depth factor (Delta)

μ

Poisson’s ratio (My)

σ′x

Effective pressure at stage x

Chapter 8

cu

Unconfined compression strength

cW

Adhesion between soil and wall

e

Eccentricity

Fφ

Factor of safety in terms of friction angle

fmax

Maximum compressive stress

fmin

Minimum compressive stress

Fs

Factor of safety

H

Height of wall

H0

Height of unsupported clay

K

Coefficient of lateral pressure

K0

Coefficient of earth pressure at rest

Ka

Coefficient of active earth pressure

Kf

Coefficient of earth pressure at failure

Kp

Coefficient of passive earth pressure

L

Length of slip surface

Mmax

Maximum bending moment

M0

Overturning moment

MR

Resisting moment

Pa

Active force

Pp

Passive force

PW

Force of water in tension crack

R

Force on wedge

T

Tension force in tie rod

zc

Pile penetration

z0

Depth of tension crack

δ

Angle of wall friction

φ′m

Mobilised friction

μ

Coefficient of friction

σa

Active earth pressure

σc

Cell pressure in triaxial test

σd

Deviator stress in triaxial test

σp

Passive earth pressure

σ′a

Effective active earth pressure

σ′p

Effective passive earth pressure

Average pressure

τf

Shear stress at failure

Chapter 9

Average undrained shear strength

Ae

End bearing area

As

Surface area of pile

B

Width of footing

c

Cohesion

F0

Overall factor of safety

Fs

Factor of safety

Ks

Average coefficient of earth pressure

l

Length of pile

N

Number of SPT blows

n

Number of piles

N ′

Corrected value of N

Bearing capacity factors

P

Failure load on pile

Q

Design working load

Qa

Allowable carrying capacity of pile

Qag

Allowable carrying capacity of pile group

Qe

End bearing resistance

Qf

Negative skin friction

QS

Shaft resistance

Qu

Ultimate carrying capacity of pile

Qug

Ultimate carrying capacity of pile group

qn

Net ultimate bearing capacity

qs

Safe bearing capacity

qsn

Safe net bearing capacity

qu

Ultimate bearing capacity

SPT

Standard penetration test

WP

Weight of pile

α

Adhesion factor (Alpha)

δ

Angle of friction between soil and pile (Delta)

η

Efficiency of pile group (Eta)

φ

Angle of friction

σ

Safe bearing pressure of footing

σn

Net bearing pressure of footing

Average effective overburden pressure

σ′o

Effective overburden pressure

Chapter 10

cu

Shear strength

F

Friction force

FC

Factor of safety with respect to cohesion

FS

Factor of safety

Fφ

Factor of safety with respect to friction

L

Length of slip surface

MD

Disturbing moment

MR

Resisting moment

N

Normal (or radial) component of W

NC

Stability number

R

Radius of slip circle

ru

Pore pressure ratio

S

Shear force

T

Tangential component of W

W

Weight

Chapter 11

The comprehensive list of symbols for EC7 is given in Eurocode 7. Geotechnical design Part 1: General rule. Only some of the symbols, applied in this book, are reproduced here:

Ed

Design value of the effect of actions

Edst;d

Design value of the effect of destabilizing action

Estb;d

Design value of the effect of stabilizing action

Fd

Design value of an action

Frep

Representative value of an action

Fs

Factor of safety

Gdst;d

Design value of destabilising permanent action

Gstb;d

Design value of stabilising permanent action

Qdst;d

Design value of destabilising variable action

Rd

Design value of resistance action

Sdst;d

Design value of destabilising seepage force

Td

Design value of total shear resistance

Udst;d

Design value of destabilising pore water pressure

Vdst;d

Design value of destabilising vertical action

Xd

Design value of a material property

Xk

Characteristics value of a material property

γG

Partial factor for a permanent action

γG;dist

Partial factor for a destabilising action

γG;stb

Partial factor for a stabilising action

γm

Partial factor for soil parameters (material property)

γQ

Partial factor for a variable action

γR;h

Partial factor for sliding resistance

Chapter 1

Soil Structure

Soils consist of solid particles, enclosing voids or pores. The voids may be filled with air or water or both. These three soil states (or phases) can be visualized by the enlargement of three small samples of soil.

Figure 1.1

Sample A: The soil is oven-dry, that is there is only air in the voids.Sample B: The soil is saturated, that is the voids are full of water.Sample C: The soil is partially saturated, that is the voids are partially filled with water.

The above three soil states can be described mathematically by considering:

1. Volume occupied by each constituent.

2. Mass (or weight) of the constituents.

1.1 Volume relationships

The expressions derived in this section will answer two questions:

1. How much voids and solids are contained in the soil sample?

2. How much water is contained in the voids?

In order to obtain these answers, the partially saturated sample (C) is examined. It is assumed, for the purpose of analysis, that the soil particles are lumped together into a homogeneous mass. Similarly, the voids are combined into a single volume, which is partly occupied by a volume of water. The idealisation of the sample, indicating the ­volumes occupied by the constituents, is shown diagrammatically in .