LIQUEFACTION POTENTIAL OF COHESIONLESS

SOILS IN SOUTH MUMBAI

SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS

OF THE DEGREE OF

BACHELOR OF ENGINEERING

BY

ABHIJEET ASHOK LONDHE (ROLL NO. 1110223)

MANAVENDRA NIRANJAN MULYE (ROLL NO. 1110234)

MURTAZA ABDULKADER KHANDWAWALA (ROLL NO. 1110220)

PARAS PAWAN KHAITAN (ROLL NO. 1110216)

SUPERVISOR:

Prof. Dr. GANESH S. KAME

DEPARTMENT OF CIVIL ENGINEERING

Anjuman-i-Islams

MOHAMMED HAJI SABOO SIDDIK COLLEGE OF ENGINEERING

AFFILIATED TO UNIVERSITY OF MUMBAI

2014-2015

i

CERTIFICATE

This is to certify that the project entitled Liquefaction Potential of

Cohesionless Soils in South Mumbai is a bonafide work of

Abhijeet Ashok Londhe (Roll No. 1110223)

Manavendra Niranjan Mulye (Roll No. 1110234)

Murtaza Abdulkader Khandwawala (Roll No. 1110220)

Paras Pawan Khaitan (Roll No. 1110216)

submitted to the University of Mumbai in partial fulfillment of the

requirement for the award of the degree of Bachelor of Engineering

in Civil Engineering.

Prof. Dr. Ganesh S. Kame

Project Guide

Prof. Zaheer Khan Dr. Mohiuddin Ahmed

Head of Department Principal

Vice Principal

ii

Project Report Approval for Bachelor of Engineering

This project report entitled Liquefaction Potential of Cohesionless

Soils in South Mumbai by

Abhijeet Ashok Londhe (Roll No. 1110223)

Manavendra Niranjan Mulye (Roll No. 1110234)

Murtaza Abdulkader Khandwawala (Roll No. 1110220)

Paras Pawan Khaitan (Roll No. 1110216)

is approved for the degree of Bachelor of Engineering in Civil

Engineering.

Examiners

1.----------------------------------------

2.----------------------------------------

Date:

Place:

iii

Declaration

I declare that this written submission represents my ideas in my own words and where others'

ideas or words have been included, I have adequately cited and referenced the original sources. I

also declare that I have adhered to all principles of academic honesty and integrity and have not

misrepresented or fabricated or falsified any idea/data/fact/source in my submission. I understand

that any violation of the above will be cause for disciplinary action by the Institute and can also

evoke penal action from the sources which have thus not been properly cited or from whom

proper permission has not been taken when needed.

Abhijeet Ashok Londhe

(Roll No. 1110223)

Manavendra Niranjan Mulye

(Roll No. 1110234)

Murtaza Abdulkader Khandwawala

(Roll No. 1110220)

Paras Pawan Khaitan

(Roll No. 1110216)

Date:

iv

Acknowledgement

We are grateful to present our project. Apart from our efforts, the success of this project largely

depends upon the encouragement and motivation of numerous professors and professionals who

have assisted and guided us with their erudite judgements and opinions, and their well wishes.

We are greatly indebted to our guide Prof. Dr. Ganesh S. Kame for his immense support, driving

force and inspiration. Without his excellent acumen, this project would not have been what it is.

He has provided us with his experience and deep knowledge to the subject.

We would also express our gratitude to our principal Dr. Mohiuddin Ahmed and our respected

Head of the Department Prof. Zaheer Khan for the convenience and facilities which we received

in the college.

Lastly, we would like to thank all the staff of Civil Engineering Department for their direct or

indirect contribution in making this project so successful.

Last but not list we are obliged to Head of Department, Principal and Management to avail us

financial support for successful development of the experimental set up.

We are also highly obliged to the University of Mumbai for availing us minor research grant for

further development of the experimental model on Soil Liquefaction.

Abhijeet Ashok Londhe

Manavendra Niranjan Mulye

Murtaza Abdulkader Khandwawala

Paras Pawan Khaitan

v

Abstract

The use of quicksand as a convenient plot device in television and movies often leads to

misconceptions, even among students taking introductory geotechnical engineering courses.

Because quicksand is a familiar natural phenomenon, exploring the underlying mechanisms

provides an exceptional opportunity for student learning.

Liquefaction is a state of saturated cohesionless soil when its shear strength is reduced to zero

due to increase in pore water pressure. It occurs due to the vibrations and horizontal accelerations

during an earthquake which raises the water table and even settles the sand grains in voids (if

present). Thus the soil starts behaving like a liquid. The same output is achieved when these

pores are filled by water externally (in the form of rainfall particularly). The output in either case

is termed quick sand in common language and liquefied soil technically.

Now during an earthquake, the upward propagation of shear waves through the ground generates

shear stresses and strains that are cyclic in nature. If a cohesionless soil is saturated, excess pore

pressures may accumulate during seismic shearing and lead to liquefaction. Liquefaction is most

commonly observed in shallow, loose, saturated deposits of cohesionless soils subjected to

strong ground motions in large-magnitude earthquakes. Unsaturated soils are not subject to

liquefaction because volume compression does not generate excess pore pressures. Liquefaction

and large deformations are more likely with contractive soils while cyclic softening and limited

deformations are associated with dilative soils. The steady-state concept demonstrates how the

initial density and effective confining stress affect the liquefaction characteristics of a particular

soil.

The model presenting demonstrates Soil Liquefaction conditions in a laboratory. The model is

capable of measuring the pore water pressure at which any given soil layer can liquefy. Thus, the

liquefaction theory and equations can be proved and executed with the help of the model.

Furthermore, the time required for different water pressure to liquefy sand can also be calculated

by varying the pressure. The resultant study and a theory are deduced to calculate Liquefaction

potential of any place having cohesionless soil.

vi

TABLE OF CONTENTS

CHAPTER

No. CONTENT PAGE No.

CERTIFICATE i

B.E. PROJECT REPORT APPROVAL SHEET ii

DECLARATION iii

AKNOWLEDGEMENT iv

ABSTRACT v

TABLE OF CONTENTS vi

1 INTRODUCTION

1.1 General 1

1.1.1 Liquefaction-Definition 1

1.1.2 Scope of Work Presented 2

1.1.3 Scope of Future Work 2

1.2 Review of Literature 2

1.2.1 General 2

1.2.2 Paleoseismic Behaviour of Soils 3

1.2.3 Liquefaction in Silty Soils 4

1.2.4 Liquefaction Susceptibility 4

1.3 Concept of Soil Liquefaction 5

1.3.1 General 5

1.3.2 Fundamentals of Soil Liquefaction 5

1.4 Concept of Piezometer 7

1.5 Girgaum Beach 8

2 AIMS AND OBJECTIVE

2.1 Aim 9

vii

2.2 Objective 10

3 METHODOLOGY

3.1 Soil Testing 11

3.1.1 Specific Gravity by Density Bottle Method 11

3.1.2 Sieve Analysis 13

3.1.3 Void Ratio 16

3.2 Setup For Soil Liquefaction Demonstration 17

3.2.1 Apparatus 18

3.2.2 Procedure to Perform the Experiment 20

4 PARAMETRIC STUDY

4.1 Introduction 21

4.2 Observations and Calculations 22

4.2.1 Specific Gravity by Density Bottle Method 22

4.2.2 Grading of Soil 23

4.2.2.1 Conclusion of Grading of Soil 24

4.3 Pressure Head at Liquefaction 24

4.3.1 Theoretical Calculation 24

4.3.2 Observation 25

4.3.3 Conclusion 25

4.4 Time Taken For Liquefaction by Varying Discharge 26

4.4.1 Procedure 26

4.4.2 Observation 26

4.4.3 Conclusion 27

5 GROUND IMPROVEMENT TECHNIQUES

5.1 Vibroflotation 28

5.2 Stone Columns 28

5.3 Compaction 30

viii

5.4 Compaction Grouting 30

5.5 Dynamic Compaction 31

5.6 Vibrocompaction 32

5.7 Drainage Techniques 33

5.7.1 Need For Improvement 34

5.7.2 Classification of Ground Modification Techniques 34

5.7.3 Suitability & Feasibility 35

5.8 Wick Drains 36

5.9 Deep Soil Mixing 37

5.10 Scope of Future Work 38

5.10.1 Potential of Liquefaction of Other Areas 38

5.10.2 Earthquake vs. Pressure Relation 38

5.10.3 Implementation of Shake Table 38

CONCLUSION 39

REFERENCES 41

APPENDIX 43

ix

CONTENT OF TABLES

TABLE No. CONTENT PAGE No.

3.1 Weight of Soil and Size 14

4.1 Observation Table for Density Bottle method 22

4.2 Grading of Soil 23

4.3 Observation Table for Time Measured 26

x

CONTENT OF FIGURES

FIGURE No. CONTENT PAGE No.

1.1 Stresses in Soil Element 5

1.2 Scheme of Piezometer 7

1.3 Photograph Showing Girgaum Beach 8

3.1 Density Bottle 11

3.2 Grain Size Distribution Curve 14

3.3 Photograph Showing Laboratory Model 17

3.4 Scheme of Laboratory Model 19

4.1 Grain Size Distribution Tested Curve of Soil 23

4.2 Pressure vs Time Curve 27

5.1 Vibroflotation 28

5.2 Stone Columns 29

5.3 Compaction Grouting 31

5.4 Dynamic Compaction 32

5.5 Vibro Compaction 33

5.6 Wick Drains 36

5.7 Deep Soil Mixing 37

xi

ABBREVIATIONS, NOTATION AND NOMENCLATURE

Symbols Nomenclature

Bulk Unit Weight of Soil

w Unit Weight of Water

sat Saturated Unit Weight of Soil

d Dry Unit Weight of Soil

Submerged Unit Weight of Soil

Angle of Shear Failure

' Effective Stress

Density of Water

ud Pore Water Pressure

g Acceleration due to gravity

G Specific gravity of Soil

e Void Ratio

n Porosity

Introduction

1

Chapter-1

Introduction

1.1 General

1.1.1 Liquefaction Definition

During an earthquake, a building may collapse due to various factors, namely, structural failure

of building, failure of foundation of the building or collapse of some other structure on the

building. In addition to these, the building which structurally sound, may fail due to liquefaction

of the soil below its foundation.

Soil Liquefaction is a phenomenon similar to quick sand, the only difference being that

liquefaction takes place during an earthquake. Liquefaction is defined as the phenomenon of loss

of shear strength of a saturated cohesionless soil due to increase in pore-water pressure as a result

of an earthquake. When a soil liquefies, any object placed on it having density mare than

liquefied soil, sinks into the soil as the soil has no shear strength. Therefore, all the structures

Chapter No: 1

2

standing on such a soil are prone to damage. The foundations of the structure sinks and the

structure may collapse. It is, hence, necessary to check the strata for probability of liquefaction

before designing the foundation of structures.

1.1.2 Scope of Work Presented

There is no direct relation between earthquake intensity and the pressure developed in the soil.

This project is based on establishing a discreet relationship between earthquake and pressure.

The magnitude of pressure and time taken by soil strata for liquefaction can be depicted. Efforts

can be made to match the inlet pressure to the magnitude of earthquake.

Comparisons can be made between the pressure readings obtained for same soil by implementing

various remedial measures. Also, a suitable remedy can be suggested for a particular soil

according to the site conditions and strata of the region. This model can also give liquefaction

potential of different soils from different regions.

1.1.3 Scope of Future Work

There is scope to connect a shake table to the current model and obtaining the pressure reading

without pumping, design a stable structure and implement compaction and drainage techniques

in model for densifying the soil. We also wish to have a comparative study of different soils of

Mumbai and classify regions into various zones of liquefaction.

1.2 Review of Literature

1.2.1 General

Any structure whether a building or a bridge ultimately rests on soil. Hence the stability of the

structure is largely influenced by type of soil. Soil is broadly classified as sand and clay. Clayey

soils have cohesion which influences shear strength of the soils. However, sand is cohesionless.

Hence the chance of collapse due to foundation failure is a possibility for construction in sandy

Introduction

3

soils.

1.2.2 Paleoseismic Behaviour of Soils

Considering the limited knowledge on the liquefaction behaviours in the Wenchuan 8.0

earthquake, the liquefaction characteristics are discussed through detailed site investigation and

analyses of corresponding hydrological, geologic and in-situ tests for the specific sites. The

analytical results indicate that the distribution of the liquefaction phenomena in the event is vast

with the region covered by length of 500 km and width of 200 km, but the liquefaction

distribution is rather non-uniform. The liquefaction is mainly located in the area of a rectangle

with 160 km in length and 60 km in width; and it is distributed principally in the 6 belts, which

are consistent with the local hydrological and geotechnical conditions. Moreover, three salient

characteristics of the liquefaction behaviours that are different from the previous earthquakes are

discovered by the investigation. It is shown that:(1) Liquefaction phenomena are observed within

the regions of seismic zone with intensity VI, which has not been documented previously in

Mainland of China.10 such liquefaction sites in 5 different areas are confirmed and in 2

liquefaction sites among which the buildings are damaged directly due to the liquefaction. (2)

The liquefaction phenomena in deep soils, i.e. more than 20 m in depth, occur in the shock, and

the macro-phenomena of more than 10 m water ejection in 4 different villages are observed; and

the in-situ tests for the specific sites verify the judgment. (3) The characteristics show that the

gravel soils liquefy in the shock; and the in-situ tests for the specific sites verify the reality of

such behaviours. Also the synthetic analyses of sand ejection, duration of waterspout and

corresponding geotechnical information all demonstrate that the gravel soil liquefaction

behaviours are considerable in this earthquake.

Liquefaction features can be used in many field settings to estimate the recurrence interval and

magnitude of strong earthquakes through much of the Holocene. These features include dikes,

craters, vented sand, sills, and laterally spreading landslides. The relatively high seismic shaking

level required for their formation makes them particularly valuable as records of strong paleo-

earthquakes. This state-of-the-art summary for using liquefaction-induced features for

paleoseismic interpretation and analysis takes into account both geological and geotechnical

engineering perspectives.

Chapter No: 1

4

Two independent methods for estimating prehistoric magnitude are discussed briefly. One

method is based on determination of the maximum distance from the epicenter over which

liquefaction-induced effects have formed. The other method is based on use of geotechnical

engineering techniques at sites of marginal liquefaction, in order to bracket the peak

accelerations as a function of epicentral distance; these accelerations can then be compared with

predictions from seismological models.

1.2.3 Liquefaction in Silty Soils

According to Desmond Andrews and Geoffrey Martins, simple criteria based on key soil

parameters that help partition liquefiable and non-liquefiable silty soils. A brief review of the

physical characteristics of silts and clays is first given to help clarify some misconceptions about

silty soils. Clay content and liquid limit are then considered as two key soil parameters that

help partition liquefiable and non-liquefiable silty soils. Several case histories are presented that

illustrate the applicability of using clay content as a key soil parameter. Attention is drawn to

an analogy between the liquid limit and the shear strength of a soil. This analogy is expanded to

show that the liquid limit can be regarded as a key soil parameter that gives a relative measure

of liquefaction susceptibility. Inadequacies of basing criteria for liquefaction of silty soils on just

one key parameter are finally discussed, leading to the promotion of simple criteria for

liquefaction of silty soils, utilising together both the clay content and the liquid limit soil

parameters.

1.2.4 Liquefaction Susceptibility

Aminaton Marto and Tan Choy Soon state that liquefaction susceptibility of a cohesionless soil

is based on the complex structure of soil and the behaviour of loading on that soil. The

developments of liquefaction susceptibility evaluation in last 40 decades are included. Modified

Chinese Criteria is the best known indicator which globally recognized. Due to the existing

literature gaps of liquefaction susceptibility of fine soils and the deviation of actual liquefaction

cases in past earthquake, re-examination and modification is essential to ensure the usability of

Modified Chinese Criteria. The controversy and confusion of the fine grained soils behaviour

Introduction

5

after being disturbed by cyclic load is complex. The use of clay fraction as a controlling

parameter is the main contribution of inaccurate in the evaluation. Plasticity index is the most

suitable controlling parameter to replace the clay fraction in Modified Chinese Criteria. Plasticity

index can confidently distinguish the fine grained soils behavior for the ease of assessment.

Fine grained soil could be either clay-like which expected to be cyclic softening or sand-like

that susceptible to liquefaction phenomena. With this the cyclic behavior of fine grained soils are

well understood and this lead to a more precise and confident output. Thus, Chinese Criteria

should replace fine percentage with plasticity index in the assessment.

1.3 Concept of Liquefaction

1.3.1 General

The term Soil Liquefaction was introduced by Arthur Cassagrande. Liquefaction is a state of

saturated cohesionless soil when its shear strength is reduced to zero due to pore water pressure

caused by the vibration during an earthquake. The soil starts behaving like a liquid.

1.3.2 Fundamentals of Soil Liquefaction

To understand the liquefaction phenomenon, let us consider a soil element of soil deposit at a

depth of z below the ground surface (G.S.). Let the depth of water table (W.T.) be h below the

ground surface.

Fig 1.1 Stresses in Soil Element

Chapter No: 1

6

Effective stress at a depth z below the ground surface is given by:

' = h + sat (z-h) w (z-h)

' = h + (z-h)

where, is submerged density = sat w

The shear strength of a cohesionless soil is due to internal friction and is given by:

S = tan

When the soil deposit is subjected to ground vibrations, it tends to compact and decrease in

volume. However if the drainage of pore water is prevented, this tendency to decrease in volume

results in an increase in pore water pressure.

Let ud be the excess dynamic pore water pressure developed due to ground

vibration. Dynamic shear strength is expressed as:

Sd = (-ud) tan

Dynamic shear strength will become zero when

= ud

Thus, liquefaction occurs when dynamic pore water pressure is equal to effective stress.

It may be noted that the rise of pore water pressure reduces the shear strength of the soil. If the

soil loss in shear strength is not complete, partial liquefaction is said to have taken place. In this

case, the shear strength of soil is not completely zero but is very less. In either case, the

structures made on the soil are vulnerable to failure.

Large settlements occur after liquefaction and the structure resting on the sand starts sinking.

This sinking continues to take place until the sand remains liquefied. It may be summarised that

for liquefaction to occur, all the following five conditions must be satisfied: -

1) The soil is cohesionless

2) The soil is loose

Introduction

7

3) The soil is saturated

4) There is shaking of ground of required intensity and duration

5) The undrained conditions are developed due to its limited permeability

It is worth noting that liquefaction can occur in soil deposits at any depth where these conditions

are satisfied. Once liquefaction occurs at a particular depth, the flow of water occurs in upward

direction, and it may cause an indirect liquefaction in the soil layers above.

1.4 Concept of Piezometer

Piezometer is the simplest form of manometer which is tapped into wall of pressure conduit for

the purpose of measuring pressure. Though effective in many purposes, piezometer is not

practical use to lighter liquids with large pressure and cannot be used to measure gas pressure. A

piezometer is a device used to measure liquid pressure in a system by measuring the height to

which a column of the liquid rises against gravity.

Fig 1.2 Scheme of Piezometer

From the figure 1.2, three piezometers A, B and C are attached to a pressure conduit at bottom,

top and side respectively. The column of liquid at A, B and C will rise at same level above A

indicating a positive pressure at M. Also, the piezometer D measures the negative pressure at N.

Chapter No: 1

8

The pressure is calculated by the equation:

P = g h

Where, P is pressure by which fluid is flowing,

is density of liquid used,

g is acceleration due to gravity &

h is height of water in water column from centre of the conduit.

If experiment is conducted using water then = 1000 kg/m3

If another fluid of different specific gravity (s) is then pressure is given by

P = s g h

1.5 Girgaum Beach

Fig 1.3 Photograph showing Girgaum Beach

Girgaum Beach, commonly known as just Chaupati (pronounced as chow-patty), is one of the

most famous public beaches adjoining Marine Drive in the Girgaum area of Mumbai, India. It

has a 4.3 km long coast line. The beach is famous for Ganesh Chaturthi celebrations when

Introduction

9

hundreds of people from all over Mumbai come to immerse the idols of Lord Ganapati in the

Arabian Sea. It is also one of the many places in the city where the Ramlila is performed on a

stage every year. An effigy of Ravan, erected on the sand, is burnt by the end of the 10-day

performance. One can find several bhelpuri, panipuri, ragda patties and pav bhaji vendors on

the beach. It is also a tourist spot all around the year. Youngsters from schools and colleges often

visit the place to enjoy the cool breeze and the paraphernalia. Many foreign tourists also visit this

place as an attraction.

It is in one of the most expensive parts of the city of Mumbai as it is a sea-facing neighbourhood.

There are many expensive houses along the sea coast. It is also a host to numerous expensive and

grand hotels. Saifee Hospital, one of the finest hospitals in Mumbai, is also along this coastline.

Mumbai Police Gymnasium and Tarapoor Aquarium are also in the vicinity of this area.

Being a beach it is highly susceptible to the issue studied in this project. The buildings and

structures near this beach are vulnerable to Liquefaction during an earthquake. Since the beach is

an integral part of Mumbaikars, we have considered studying the Liquefaction potential of this

place. Thus the case has been studied considering the culture of Mumbai and grandeur of the

beach.

Girgaum Beach was selected as it had numerous other advantages too. It is located very close to

the college. Access to sand of the beach is very easy. Also, the permissions required to perform

the experiment on the beach or on the sample of soil for purpose of project from the concerned

authorities are relatively less tedious because of close affinity.

Chapter No: 2

10

Chapter-2

Aims & Objectives

2.1 Aim This project demonstrates soil liquefaction phenomenon in a laboratory. This is the working

model depicting this phenomenon. The model is made with an objective of testing cohesionless

soil from any region so as to obtain the pressure reading at which the given soil liquefies. The

pressure obtained will be used to comment on the stability of existing structures as well as

constructing new structures.

2.2 Objective

This project is aimed at knowing the liquefaction probability of soils in South Mumbai. South

Mumbai is a lavish area with lot of sand as its strata. Hence, during an earthquake, it has got

the highest likelihood of liquefaction. This project is an attempt to find the odds at which the

soil in South Mumbai is safe and the earthquake at which it will liquefy.

Methodology

11

Chapter-3

Methodology

3.1 Soil Testing

3.1.1 Specific Gravity by Density Bottle Method

Aim: To find Specific gravity of soil sample by density bottle

method as per IS:2720 Part II (1980).

Apparatus: Density bottle of capacity 100 mL, Soil sample,

water and weighing machine with sensitivity of 0.01 g.

Theory: Specific Gravity of solid particles is the ratio of the

mass density of solids to that of water. It is determined

in the laboratory using the relation Fig 3.1 Density Bottle

G =

Where, M1 = Mass of empty density bottle.

Chapter No: 3

12

M2 = Mass of density bottle + Soil grains.

M3 = Mass of empty density bottle + Soil grains + water.

M4 = Mass of empty density bottle + water.

Procedure:

1) Take the Weight of clean and dry density bottle.

2) Keep about 10 15 gm of oven dried cool soil in bottle and weight (M2).

3) Cover the soil with air free distilled water from the plastic wash bottle. Give some time of

socking. A gentle heating may be required to dispel any air inside the soil. Gently stir the

soil in the density bottle by clean glass rod. Observe the temperature of the contents (oC)

in the bottle and record. Insert the stopper in the density bottle, wipe and weight (M3).

4) Empty the content of bottle, rinse thoroughly, fill it with distilled water at the same

temperature, insert the stopper, wipe dry from outside and weight it (M4).

5) Note the ridings as given in Table and at least three such observation and Calculate the

Specific Gravity using stated equation.

Precautions:

1) The soil grains whose specific gravity is to be determined should be completely dry.

2) Inaccuracies in weighting and failure to eliminate the entrapped air are the main source of

error. Both should be avoided by careful working.

3) If pycnometer is used, the cap of the pycnometer should be screwed up to the same mark

for each test.

Methodology

13

3.1.2 Sieve Analysis Aim: To grade soil depending upon their size by sieve analysis as per IS:1498 1970.

Theory: Dry sieve analysis is suitable for cohesionless soil, with little or no fines. If the sand is

sieved in wet conditions, the surface tension may cause a slight increase in the size of the particle

and the particles smaller than the aperture size may be retained on the sieve and results would be

erroneous.

Soil is sieved through a set of sieves. The material retained on different sieves is determined. The

percentage of the material retained on any sieve is given by

Pn =

Where Mn = Mass of soil retained on sieve n

M = total mass of sample.

The cumulative percentage of the material retained,

Cn = p1 + p2 + pn

Where p1, p2 etc., are the percentage retained on sieve 1, 2 etc. respectively which are coarser

the sieve n. The percentage finer than the sieve n,

Nn = 100 Cn

A graph is plotted between particle size () on X-axis and % finer on Y-axis on a semi-log graph

paper. Grading of soil is done on the basis of following chart.

Chapter No: 3

14

Fig 3.2 Grain Size Distribution Curve

The uniformity of a soil is expressed qualitatively by a term known as uniformity coefficient, Cu,

given by

Cu =

Where, D60 is particle size such that 60% of soil is finer than this size, and

D10 is particle size such that 10% of soil is finer than this size.

The general shape of particle size distribution curve is described by another coefficient known as

the coefficient of curvature (Cc)

Cc =

Where, D30 is particle size such that 30% of soil is finer than this size.

Sand with Cu of 6 or more and Cc between 1 to 3 are well graded soil.

The total weight of soil to be tested is determined by the following chart.

Table 3.1 Weight of Soil and Size

Sr. No. Maximum Size Quantity in kg

1 80 mm 60

2 20 mm 6.5

3 4.75 mm 0.5

Methodology

15

Apparatus:

1) Set of fine sieves 425, 300, 212, 150 and 75

2) Weighing balance, with accuracy of 0.1% of the mass of sample

3) Oven

4) Mechanical shaker

5) Trays

Procedure:

1) Take the portion of soil passing through 4.75 mm IS sieve. Oven dry it at 105oC to 110

oC.

Weigh it to 0.1% of the total mass.

2) Sieve through the nest of fine sieves. A minimum of ten minutes of sieving is required if

mechanical shaker is used. The sieves should be agitated so that the sample rolls in

irregular motion over the sieves. However, no particles should be pushed through the

sieve.

3) Take the material retained on each sieve and weigh them.

4) Calculate the % weight retained, % cumulative weight retained and % finer in a tabular

manner.

5) Plot a graph as mentioned in the theory.

6) Calculate Cu & Cc by plotting D10, D30 and D60.

7) Determine the grading of soil.

Chapter No: 3

16

3.1.3 Void Ratio

The void ratio of soil is defined as ratio of total volume of voids to total volume of solids, i.e.

We know,

e =

Or e =

Now, e =

Vv = e.Vs

V = Vv + Vs = e.Vs + Vs

Vs =

Porosity n is ratio of volume of voids to total volume

n =

=

=

(

=

n =

e =

Methodology

17

3.2 Setup for Soil Liquefaction Demonstration

Fig 3.3 Photograph Showing Laboratory Model

Chapter No: 3

18

3.2.1 Apparatus

1) A cubical container of inner dimensions 50 cm x 50 cm x 60 cm having no top and a

square bottom. The cube is made of Galvanized Iron (G.I.) having thickness of 1.2 mm.

One hole is made on one of the sides of dimension 35 cm x 45 cm exactly at the centre.

The hole is closed using an acrylic plate of thickness 10mm.

Description

On left hand side face of the cube a hole should be present with its centre at

a height of 5 cm from bottom for connecting a piezometer.

On back face of the cube at the bottom an arrangement should be made for

inlet/outlet of water.

2) Pressure distribution table. (PDT)

A wooden frame of dimensions exactly equal to inner dimensions of the cube is placed

inside the container at the bottom. In case some voids are present around the frame, they

are filled with white cement or any other sealing material. Section of wooden frame is

50mm x 50 mm. The hole for piezometer must pass through the frame as well. An acrylic

sheet of dimensions 49 cm x 49 cm with uniformly distributed holes of 5 mm diameter at

2 cm C/C from each hole. Thickness of acrylic sheet is 10 mm.

2) Silicon Tubes, Meter scale & Piezometer.

3) Water pump of power 0.25 to 0.5 HP and water pipes and water tanks.

4) Dummy buildings and roads made of materials having specific density more than that of

water.

5) Cohesionless sand sample which is to be tested.

6) Packing material (Eg. Wax, Thermocol, Sponge etc.)

7) Plumbing arrangement, Filter Paper and Miscellaneous.

8) Pressure Gauge of capacity to read pressure of 1 Pascal.

9) Stopwatch.

Methodology

19

Fig 3.4 Scheme of Laboratory Model

Chapter No: 3

20

3.2.3 Procedure to Perform the Experiment

1) The container is placed on a table.

2) The Pressure Distribution Table (PDT) is placed inside the container at the centre. The void

space around it is packed with packing material. Over the table Wattmans filter paper is

attached. It is made sure that all the holes are covered properly. The filter paper is placed on

the table to make sure that while the apparatus is being emptied the sand grains do not enter

the lower chamber.

3) The piezometer is connected to the box using silicon tubes. It is attached on a stand which is

placed besides the container on the table. It could also be attached to the box itself. A metre

scale is attached alongside the piezometer at a height of 5 cm from table.

4) Fill dry sand in container. Sand is filled in layers. In each layer 4 trowels of sand is filled.

After each layer the sand is tamped using tamping rod. Each layer is tamped 50 times. It can

be filled up to any height. However it is necessary to know the weight of sand filled in the

container (eg. 60 kg of sand filled up to a height of 20 cm.). Spirit level is used to make sure

the sand layer is completely level.

5) Dummy building and roads are now placed inside the box on the sand layer.

6) Water pump is connected to the box at the inlet point provided at the bottom of the box.

Pump is kept on the ground.

7) The setup is now ready for checking the liquefaction potential of soil layer.

8) The pump is started and water starts flowing inside the setup. Stop watch is started as well.

Pressure is noted on the gauge. When the dummy buildings start collapsing, sinking or

tilting the water level in the piezometer is noted immediately. As this phenomenon is

instantaneous it is very necessary to keep keen observation.

9) The pump and stop watch are turned off. Time is noted. The setup is emptied.

10) The pressure is changed with the help of regulator and the same experiment is performed

again.

Parametric Study

21

Chapter-4

Parametric Study

4.1 Introduction The parametric study was carried out as per Indian Standard Codes. The results of the parametric

studies were compared with the conditions given in codes. The results of the experiments and tests

performed on the soil are compiled as shown below. The results and conclusions drawn are within

the prescribed code limits.

Chapter No: 4

22

4.2 Observations & Calculations

4.2.1 Specific Gravity by Density Bottle Method

Table 4.1

Sr.

No.

M1

(Mass

of

empty

density

bottle.)

M2

(Mass of

density

bottle +

Soil

grains)

M3

(Mass of

empty

density

bottle +

Soil grains

+ water)

M4

(Mass of

empty

density

bottle +

water.)

Specific Gravity

G

Average

G

1 32 44 88.38 81 2.597

2.6 2 32 46 89.62 81 2.602

3 32 45 89.00 81 2.600

Result: The Specific Gravity of the soil sample is 2.6

Parametric Study

23

4.2.2 Grading of Soil

Observation:

Table 4.2

Sieve Size () Weight %weight % cumulative % finer

Retained Retained

425 105.0 21.06 21.06 78.94

300 189.5 38.01 59.08 40.92

212 160.0 32.10 91.17 8.83

150 25.5 5.11 96.29 3.71

75 16.0 3.21 99.50 0.50

0.1 2.5 0.51 100.00 0

498.5 100.00

The graph as per the observed readings:-

Fig. 4.1 Grain Size Distribution Curve of Tested Soil

0

10

20

30

40

50

60

70

80

90

0.1 1 10 100 1000

% f

ine

r

Particle Size ()

Series1

Chapter No: 4

24

D10 = 0.218 D30 = 0.272 D60 = 0.361

Cu =

=

= 1.656

Cc =

=

= 0.94

4.2.2.1 Conclusion of Grading of Soil

More than 50% of the weight of sample passes through IS sieve 4.75 mm. Also, more than 50% of

the weight of sample is retained on IS sieve of 75. Hence, it can be concluded that the sample is

coarse grained sand.

The Particle Size Distribution Curve is plotted as per procedure given in IS: 1498 1970. The

distribution curve has a very small slope at the start of the curve. However, after it crosses a particle

size of 100 m, the slope rapidly increases. This means that the soil sample contains large amount

of soil of same grading. This graph concludes that the soil is uniformly graded or made of particles

of the same size.

Moreover, Cu = 1.656 and Cc = 0.94. Hence, the soil is poorly graded. Hence the given sample is poorly graded sand.

4.3 Pressure Head at Liquefaction

4.3.1 Theoretical Calculation

Calculation of theoretical value of Hw.

Now,

Z = 20 cm

Dry density is weight of sample divided by the volume covered by the soil sample.

73.3 kg of sample is used and dimensions of sample filled would be 49 x 49 x 20 cu.cm.

Dry density d =

= 14.97 kN/m3.

Parametric Study

25

For the given sample G = 2.6

d = w

e = 1.704

sat = r

sat =

g

sat = 15.615 kN/m3

satz= wHw

Hw = 31.83 cm.

4.3.2 Observation

Height of water in the piezometer obtained from the experiment performed is 32.2 cm.

4.3.3 Conclusion

The pressure reading obtained in the model is in congruence with the theoretical reading derived

from the principle of Soil Liquefaction. The observed reading is, however, less than the

contemplated reading. This can be justified by the fact that there are certain losses due to leakage of

water from the pipe-piezometer connection and the pipe-model boundary.

The soil of Girgaum Chowpatty is susceptible to liquefaction if the above pressure is established. If

the magnitude of earthquake, at which there is a possibility of establishing this pressure, can be

found out, we can suggest weather the buildings and other structures near Girgaun Chowpatty are

safe from Liquefaction.

4.4 Time Taken For Liquefaction by Varying Discharge

4.4.1 Procedure

The pressure head of the given soil strata for liquefaction is known. It was calculated theoretically

Chapter No: 4

26

and subsequently verified by the model. So,

Head at Liquefaction (h) = 31.8 cm

Now, the discharge of water which is pumped into the soil strata is varied. The pressure gauge is

used to indicate the pressure of discharge, in kg/cm2.

Time is measured, in seconds, with the help of a stopwatch from the point of start of motor to the

point when pressure head equal to 31.8 cm is reached in the piezometer.

Three readings are taken for every 0.5 kg/cm2

variation.

4.4.2 Observation

The readings taken are tabulated below.

Table 4.3

Pressure

(kg/cm2)

Time

(sec)

Average

Time

(sec)

2

26.03

26.13 25.56

26.81

1.5

33.2

31.38 30.18

30.77

1

41.56

40.35 39.85

39.65

0.5

54.73

55.05 54.11

56.31

The graph of Pressure vs. Time in plotted.

Parametric Study

27

Fig 4.2 Pressure vs. Time Curve

4.4.3 Conclusion

Greater the pressure, less is the time taken for liquefaction. In other words, the time taken for

liquefaction of the strata is inversely proportional to the pressure of inlet discharge of water.

The pressure can be linked with magnitude of earthquake. Greater pressure implies higher

magnitude of earthquake. The observations state that the soil strata will liquefy faster for an

earthquake of greater magnitude.

When depth of strata changes, these values will change and well get another Pressure vs. Time

curve. Similarly, for different density of soils, different Pressure vs. Time curves can be expected.

If the pressure can be matched to the horizontal acceleration produced by an earthquake, it might be

possible to determine the magnitude of earthquake on a Richters Scale. For this, a shake table is

needed and the model must be analyzed for dynamic effects.

0

1

2

3

4

5

6

7

0 20 40 60 80 100 120 140 160 180

Pre

ssu

re (

kg/c

m2)

Time (Sec)

Chapter No: 5

28

Chapter-5

Ground Improvement Techniques

5.1 Vibroflotation

Vibroflotation involves the use of a vibrating probe that can penetrate granular soil to depths of

over 100 feet. The vibrations of the probe cause the grain structure to collapse thereby densifying

the soil surrounding the probe. To treat an area of potentially liquefiable soil, the vibroflot is raised

and lowered in a grid pattern. Vibro Replacement is a combination of vibroflotation with a gravel

backfill resulting in stone columns, which not only increases the amount of densificton, but

provides a degree of reinforcement and a potentially effective means of drainage.

Fig 5.1 Vibroflotation

5.2 Stone Columns As described above, stone columns are columns of gravel constructed in the ground. Stone

columns can be constructed by the vibroflotation method. They can also be installed in other

Ground Improvement Techniques

29

ways, for example, with help of a steel casing and a drop hammer as in the Franki Method. In this

approach the steel casing is driven in to the soil and gravel is filled in from the top and tamped

with a drop hammer as the steel casing is successively withdrawn.

This method can be applied to different site conditions and is still widely used due to its high

tensile load capacity, and relatively low noise and ground vibration levels.

A charge of zero-slump concrete is poured into the bottom of a steel driving pipe that is placed

vertically on the ground. A diesel-operated drop hammer is then driven on the concrete, forming a

watertight concrete plug.

The concrete plug is driven into the ground by the drop hammer. The pipe is also dragged into the

ground due to friction developed between the steel and the concrete. When the desired depth is

reached, the pipe is held in position by leadsstructures which guide and align the pile and

hammer. The hammer is then applied to the concrete, driving it outwards through the bottom of the

pile and forming a mushroom-shaped base.

At this point, a cylindrical rebar cage can be driven into the concrete if supplementary

reinforcement is desired. Additional charges of concrete are added and driven while the steel casing

is simultaneously pulled up until the shaft of the pile is formed.

Fig 5.2 Stone Columns

This particular system can also be used to enhance stability of the land around a preexisting

structure thus making it safe.

Chapter No: 5

30

5.3 Compaction

In geotechnical engineering, soil compaction is the process in which a stress applied to a soil

causes densification as air is displaced from the pores between the soil grains. When stress is

applied that causes densification due to water (or other liquid) being displaced from between the

soil grains then consolidation, not compaction, has occurred. Soil compaction is usually a

combination of both engineering compaction and consolidation so may occur due to a lack of

water in the soil, the applied stress being internal suction due to water evaporation as well as due

to passage of animal feet.

The main goal of most soil improvement techniques used for reducing liquefaction hazards is to

avoid large increases in pore water pressure during earthquake. This can be achieved by

compaction in following ways.

5.4 Compaction Grouting

Pressure grouting involves injecting a grout material into generally isolated pore or void space

of which neither the configuration nor the volume are known, and is often referred to simply as

grouting. The grout may be a cementitious, resinous, or solution chemical mixture. The

greatest use of pressure grouting is to improve geomaterials (soil and rock). The purpose of

grouting can be either to strengthen or reduce water flow through a formation. It is also used to

correct faults in concrete and masonry structures. Since first usage in the 19th century,

grouting has been performed on the foundation of virtually every one of the worlds large

dams, in order to reduce the amount of leakage through the rock, and sometimes to strengthen

the foundation to support the weight of the overlying structure, be it of concrete, earth, or rock

fill. Although very specialized, pressure grouting is an essential construction procedure that is

practiced by specialist contractors and engineers around the world. Compaction grouting is a

technique whereby a slow-flowing water/sand/cement mix is injected under pressure into a

granular soil. The grout forms a bulb that displaces and hence densifies, the surrounding soil.

Compaction grouting is a good option if the foundation of an existing building requires

improvement, since it is possible to inject the grout from the side or at an inclined angle to reach

beneath the building.

Ground Improvement Techniques

31

Fig 5.3 Compaction Grouting

5.5 Dynamic Compaction Dynamic compaction is a method that is used to increase the density of the soil when certain

subsurface constraints make other methods inappropriate. It is a method that is used to increase

the density of soil deposits. The process involves of dropping a heavy weight repeatedly on the

ground at regularly spaced intervals. The weight and the height determine the amount of

compaction that would occur. The weight that is used, depends on the degree of compaction

desired and is between 8 tonne to 36 tonne. The height varies from 1m to 30m.

The impact of the free fall creates stress waves that help in the densification of the soil. These

stress waves can penetrate up to 10m. In cohesionless soils, these waves create liquefaction that

is followed by the compaction of the soil, and in cohesive soils, they create an increased amount

of pore water pressure that is followed by the compaction of the soil. Pore water pressure is the

pressure of water that is trapped within the particles of rocks and soils.

The degree of compaction depends on the weight of the hammer, the height from which the

hammer is dropped, and the spacing of the locations at which the hammer is dropped. The initial

weight dropping has the most impact, and penetrates up to a greater depth. The following drops,

if spaced closer to one another, compact the shallower layers and the process is completed by

compacting the soil at the surface.

Chapter No: 5

32

Fig 5.4 Dynamic Compaction

Densification by dynamic compaction is performed by dropping a heavy weight of steel or

concrete in a grid pattern from heights of 30 to 100 ft. It provides an economical way of

improving soil for mitigation of liquefaction hazards. Local liquefaction can be initiated beneath

the drop point making it easier for the sand grains to densify. When the excess pore water

pressure from the dynamic loading dissipates, additional densification occurs. As illustrated in

the photograph, however, the process is somewhat invasive; the surface of the soil may require

shallow compaction with possible addition of granular fill following dynamic compaction.

5.6 Vibro Compaction Vibro compaction is a ground improvement technique that densifies clean, cohesionless granular

soils by means of a downhole vibrator.

The vibrator is typically suspended from a crane and lowered vertically into the soil under its

own weight. Penetration is usually aided by water jets integrated into the vibrator assembly.

After reaching the bottom of the treatment zone, the soils are densified in lifts as the probe is

extracted. During vibro compaction, clean sand backfill is typically added at the ground surface

to compensate for the reduction in soil volume resulting from the densification process. The

vibratory energy reduces the inter-granular forces between the soil particles, allowing them to

move into a denser configuration, typically achieving a relative density of 70 to 85 percent. The

treated soils have increased density, friction angle and stiffness. Compaction is achieved above

Ground Improvement Techniques

33

and below the water table.

The improved soil characteristics depend on the soil type and gradation, spacing of the

penetration points and the time spent performing the compaction. Generally, the vibro

compaction penetration spacing is between 6 feet and 14 feet, with centers arranged on a

triangular or square pattern. Compaction takes place without setting up internal stresses in the

soil, thus ensuring permanent densification.

Installing compaction piles are a very effective way of improving soil. Compaction piles are

usually made of prestressed concrete or timber. Installation of compaction piles both densifies

and reinforces the soil. The piles are generally installed in a grid pattern and are generally driven

to depth of up to 60ft.

Fig 5.5 Vibro Compaction

5.7 Drainage Techniques Liquefaction hazards can be reduced by increasing the drainage ability of the soil. If the pore

water within the soil can drain freely, the build-up of excess pore water pressure will be reduced.

Drainage techniques include installation of drains of gravel, sand or synthetic materials.

Chapter No: 5

34

Synthetic wick drains can be installed at various angles, in contrast to gravel or sand drains that

are usually installed vertically. Drainage techniques are often used in combination with other

types of soil improvement techniques for more effective liquefaction hazard reduction.

5.7.1 Need for Improvement When a project encounters difficult foundation conditions, possible alternate solutions are:

Avoid the particular site

Design the planned structure accordingly.

Use a soft foundation supported by piles, design a very stiff structure which is not

damaged by settlements

Remove and replace unsuitable soils.

Attempt to modify the existing ground.

5.7.2 Classification of Ground Modification Techniques

Mechanical Modification:

Soil density is increased by the application of mechanical force, including compaction of

surface layers by static vibratory such as compact roller and plate vibrators.

Hydraulic Modification:

Free pore water is forced out of soil via drains or wells. Course grained soils; it is

achieved by lowering the ground water level through pumping from boreholes, or

trenches. In fine grained soils the long term application of external loads (preloading) or

electrical forces (electrometric stabilization)

Physical and chemical modification:

Stabilization of the soil is done by physical mixing of adhesives with surface layers or

columns of soil. Adhesives may include natural soils, industrial byproducts or waste,

materials, cementations or other chemicals which react with each other and/or the ground.

When adhesives are injected via boreholes under pressure into voids within the ground or

between it and a structure the process is called grouting.

Ground Improvement Techniques

35

Soil stabilization by heating and by freezing the ground is considered thermal methods of

modifications.

Modification by inclusions and confinement:

Reinforcement by fibers, strips bars meshes and fabrics imparts tensile strength to a

constructed soil mass.

In-situ reinforcement is achieved by nails and anchors. Stable earth retaining structure

can also be formed by confining soil with concrete, steel or fabric elements.

5.7.3 Suitability &Feasibility

The choice of a method of ground improvement for a particular object will depend on the

following factors.

Type and degree of improvement required

Type of soil, geological structure, seepage conditions

Cost

Availability of equipment and materials and the quality of work required

Construction time available

Possible damage to adjacent structures or pollution of ground water resources

Durability of material involved ( as related to the expected life of structure for a given

environmental and stress conditions)

Toxicity or corrosivity of any chemical additives.

Reliability of method of analysis and design.

Feasibility of construction control and performance

measurements (If soil is moist, freezing is applicable to all type of

soil.)

Chapter No: 5

36

5.8 Wick Drains (Prefabricated Vertical Drains, Vertical Strip Drains)

Wick drains, also known as Prefabricated Vertical Drains (PVD) and Vertical Strip Drains

(VSD), are a ground improvement technique that provides drainage paths for pore water in soft

compressible soil, using prefabricated geotextile filter-wrapped plastic strips with molded

channels. A hollow mandrel is mounted on an excavator or crane mast. The wick drain material,

contained on a spool, is fed down through the mandrel and connected to an expendable anchor

plate at the bottom of the mandrel. A vibratory hammer or static method is used to insert the

mandrel to design depth. The mandrel is then extracted leaving the wick drain in place. The wick

drain is then cut at the ground surface, a new anchor plate is connected to it and the mandrel

moved to the next location. A pattern of installed vertical wick drains provides short drainage

paths for pore water, thereby accelerating the consolidation process and the construction

schedule.

Fig 5.6 Wick Drains

Ground Improvement Techniques

37

5.9 Deep Soil Mixing

An effective way to conduct Soil liquefaction mitigation is through seep soil mixing (DSM) or

increasing the height of strata. The DSM method involves boring through the soil with a

specialized, large-diameter auger (between three and 12 feet) equipped with mixing paddles.

Once the auger reaches the appropriate depth, it is filled with cement that is released through

holes on the core of the auger. As the cement fills the hole, the mixing paddles combine it with

the surrounding soil to create a solidified, underground column.

In addition to its uses in building construction, DSM is also utilized in projects that require

sludge stabilization such as Brownfield redevelopment and industrial cleanup. In these cases,

DSM technicians can use soil reagents such as fly ash or harder, less porous soil types to reduce

the moisture level of the sludge.

DSM can also be used for chemical remediation. By solidifying contaminated soil with either

cement or other binders, the contaminants in the soil are isolated and solidified, preventing them

from seeping into nearby water supplies. New developments include the use of zero-valet iron,

carbon and special clays to create solid soils and reduce the impact of liquefaction. Traditional

cement columns and solidifying agents are both effective methods of barrier construction to

protect environmentally sensitive areas from infiltration, or to stabilize areas prone to soil

erosion.

Fig 5.7 Deep Soil Mixing

Chapter No: 5

38

5.10 Scope of Future Work

5.10.1 It is aimed to study liquefaction potential of cohesion less soils in South Mumbai.

Similarly, the liquefaction potential of other areas can also be studied.

5.10.2 Comparison of results obtained using mathematical technique and experimental findings.

Establishing relationship between inlet pressure and magnitude of earthquake. Comparing

Static and Dynamic Analysis.

5.10.3 To model the liquefaction phenomenon under the action of earth motion during an

earthquake, it is also aimed to run the model on shake table. The shake table

demonstration is aimed to be performed at the heavy structural engineering laboratory,

Indian Institute of Technology Bombay, Mumbai or Sardar Patel College of Engineering,

Andheri, Mumbai.

Conclusion

39

Chapter-6

Conclusion

Liquefaction is a state of saturated cohesionless soil when its shear strength is reduced to zero

due to pore water pressure caused by the vibration during an earthquake. The soil starts behaving

like a liquid. During an earthquake, the upward propagation of shear waves through the ground

generates shear stresses and strains that are cyclic in nature. If a cohesionless soil is saturated,

excess pore pressures may accumulate during seismic shearing and lead to liquefaction.

Liquefaction is most commonly observed in shallow, loose, saturated deposits of cohesionless

soils subjected to strong ground motions in large-magnitude earthquakes. Unsaturated soils are

not subject to liquefaction because volume compression does not generate excess pore pressures.

Liquefaction and large deformations are more likely with contractive soils while cyclic softening

and limited deformations are associated with dilative soils. The steady-state concept

demonstrates how the initial density and effective confining stress affect the liquefaction

characteristics of a particular soil.

Chapter No: 6

40

In the previous study, model which demonstrates Soil Liquefaction conditions in a laboratory

was successfully developed.

The model is capable of measuring the pore water pressure at which any given soil layer can

liquefy. A piezometer attached to the model gives the exact reading of pressure at which the soil

liquefies. Thus, the liquefaction theory and equations can be proved with the help of our model.

The model is basically static demonstration of liquefaction with simulation of the effect of

earthquake. However, dynamic behavior of the model is yet to be tested.

In the present study, the model was enhanced to elicit more information about the phenomenon

of liquefaction. The developed model has the attribute of varying pressure of influent liquid. A

pressure gauge affixed to the model measures the exact pressure of the flow in kg/cm2. This can

help comprehend the effects of earthquakes of different magnitude on the same soil strata.

Higher the pressure of inflowing liquid, higher is the magnitude of earthquake which is

simulated. It is also possible to measure the time taken by the soil to liquefy. With the help of a

stopwatch, time can be recorded when the pore water pressure at liquefaction is reached in the

piezometer. Greater the magnitude of the earthquake, lesser will be the time taken for

liquefaction.

Using this data, it is possible to contemplate whether the given soil will liquefy or not for a

particular magnitude of earthquake.

References

41

Chapter-7

References

Bureau of Indian Standards

1. IS: 2720 Part 3 1980, Determination of Specific Gravity for fine-grained soils.

2. IS: 1498 1970, Classification and identification of soils for general engineering purposes.

3. Arora K. R., Soil Mechanics and Foundation Engineering.

International Publications

1. Kaplan Alisha, Soil Liquefaction, Ph. D Thesis, Georgia Institute of Technology, USA.

2. Yuan Xiaoming, Cao Zhenzhong, Sun Rui, Preliminary Research on Liquefaction,

Institute of Engineering Mechanics, China.

3. Stephen F. Obermeier, Paleoseismic Analysis of Liquefaction, USA.

4. Desmond C. Andrews, Geoffrey R. Martin, Liquefaction Criteria of Silty Soils,

Chapter No: 7

42

University of South California, USA.

6. Wei F. Lee, Kenji Ishihara, Chun Chi-Chen, Liquefaction of Silty Sand Taiwan Case

Study, Japan.

7. Aminaton Marto,Tan Choy Soon, Liquefaction Susceptibility, Malaysia.

Website

1. http://nptel.ac.in

Website of webinars by Professors of Indian Institute of Technology, India.

Appendix

43

Chapter-8

Appendix

Technical Terms

Cohesion: It is the attraction or bonding force between fine grained soils that creates shear strength.

Consolidation: The compression of a saturated soil under steady state pressure due to expulsion of water from soil.

Effective size: The size of the particle elements such that only 10% particles are finer than this size.

Effective stress: It is the nominal stress transmitted through the particle to particle in contact with the soil. It controls the shear strength of the soil.

Grouting: It is a process in which holes are drilled in soil or rock and grout (mixture of cement and water) is injected in the hole.

Pore pressure: It is the water pressure developed in voids of a soil mass. The shear strength is

Chapter No: 8

44

reduced due to increase in pore pressure.

Shear Strength: It is the ability of the soil to resist the stresses developed within a soil mass as a

result of loading imposed onto the soil. It is the maximum resistance offered just before failure of

structure.

Sieve: It is a pan having a screen or mesh bottom. It is used to separate particles of soil into various sizes.

Soil: Refers to sand which is a coarse grained soil whose particles range from 0.075mm to 4.75mm. Void ratio: It is the ratio of volume of voids to volume of soils.