Page 1 of 7

Journal for Studies in Management and Planning

Available at

http://edupediapublications.org/journals/index.php/JSMaP/

e-ISSN: 2395-0463

Volume 02 Issue 10

October 2016

Available online: http://edupediapublications.org/journals/index.php/JSMaP/ P a g e | 39

Study on the Behaviour of Granular Columns in Lime Stabilized Clay

Marupaka Aravind ; G.Venkataratnam

1M.Tech. (Geotechnical Engineering) Aurora Scientific and Technology and Research academy,

Hyderabad

2Professor, Department of Civil Engineering Aurora Scientific and Technology and Research

academy, Hyderabad

ABSTACT

The ground engineering emerged out of a

great need to improve the unsuitable and

difficult grounds. Soft grounds, expansive

soils, collapsible soils, dispersive soil etc.

form the difficult and unsuitable ground

conditions. Several foundation techniques

were emerged due to continuous efforts

made by various investigators all over the

world. Among the difficult ground problems

soft clays occupied large tracts of coast lines

of many world nations. These soils are

characterized by high compressibility, water

content and low shear strength making them

unsuitable for any construction purpose.

Stone columns were introduced in 1970’s

with a view to provide pervious reinforcing

pins which provide stiffness to the clay bed

while facilitating drainage. This foundation

technique could accommodate the

considerable settlements due to their

flexibility and the settlements could be

adjusted if provision is made for this

purpose. The present work is taken up to

study the influence of initial clay consistency

on the performance of single and group of

stone columns in soft clay and in lime

stabilized clay. The soft clay prepared from

locally available black cotton soil has

become highly workable with improved

stiffness upon 3% lime stabilization. The

undrained shear strength for prepared clay

is varied from 2.8 to 8 kPa at different

consistencies of investigation whereas for

lime treated clay, it is varied from 90 kPa

to140 kPa at 28 days curing period. The

ultimate load capacity of single or group of

stone columns is increased by multifold upon

3% lime stabilization of clay bed. The

increase is varying from 8-38 times

compared to the stone column in virgin clay

with controlled settlements.

INTRODUCTION

The ground engineering emerged out of a

great need to improve the unsuitable and

difficult grounds. Soft grounds, expansive

soils, collapsible soils, dispersive soil etc.

form the difficult and unsuitable ground

conditions. Several foundation techniques

were emerged due to continuous efforts

made by various investigators all over the

world. Among the difficult ground problems

soft clays occupied large tracts of coast lines

of many world nations. These soils are

characterized by high compressibility, water

content and low shear strength making them

unsuitable for any construction purpose. In

view of enormous economic activity along

the coast lines all over the world, there lies a

need to improve these clay beds for building

high end infrastructure facilities. In this

direction, efforts were made by various

investigators to develop suitable ground

Page 2 of 7

Journal for Studies in Management and Planning

Available at

http://edupediapublications.org/journals/index.php/JSMaP/

e-ISSN: 2395-0463

Volume 02 Issue 10

October 2016

Available online: http://edupediapublications.org/journals/index.php/JSMaP/ P a g e | 40

improvement/foundation techniques. The

most popular foundation techniques include

preloading with vertical drains, electro- osmotic dewatering, pile foundations, stone

columns and deep lime/cement mixing. The

hydraulic modification by preloading and

electro-osmotic drainage is based on the

fundamental consolidation theory. Piles can

be suitable foundation for site conditions

having shallow stiff/hard stratum below the

top soft clay. Deep lime/cement mixing is

adopted when considerable thickness of clay

bed is to be modified to overcome the

compressibility and low shear strength, so

that it can support high class infrastructure.

Stone columns were introduced in 1970’s

with a view to provide pervious reinforcing

pins which provide stiffness to the clay bed

while facilitating drainage. This foundation

technique could accommodate the

considerable settlements due to their

flexibility and the settlements could be

adjusted if provision is made for this

purpose. Despite their wide use across the

world, several investigators reported their

skepticalbehavior at certain site conditions;

especially when the ground is too soft

having Undrained Shear Strength value less

than 20kPa. In order to overcome this

situation, an attempt is made to pre-stabilize

the soft clay using 3% lime as arrived from

preliminary testing. Single and group of

stone columns were load tested in test tanks

at different initial consistencies without and

with lime stabilization and the behavior is

compared.

Consistency limits

In most cases the effect of lime on the

plasticity of clay soil is more or less

instantaneous, the calcium Ions from the

lime causing a reduction in plasticity, the

soils becoming more friable and more easily

worked. The clay particles undergo

flocculation to form aggregates. The

aggregates behave like particles of silt. Very

small quantities of lime are required to bring

about these changes in plasticity. Generally

the amount needed varies from 1 to 3%

depending on the amount and type of clay

minerals present in soil.

Strength and deformation

The amount of strength increase in a clay

soil that can be produced by adding lime is

dependent on the pozzolans present. When

the desirable pozzolans are available, they

react readily with lime to improve the

strength of soil-lime mixtures. Hence clays

generally show a significant increase in

strength when lime is used for stabilization.

As can be inferred from the above, the

unconfined compressive strength of lime- treated soil develops rapidly with increasing

addition of lime until an optimum lime

content is reached beyond which the strength

continues to increase at a reduced rate or

begins to decline.

LITERATURE REVIEW

Mitchell and Hooper (1961) proposed that

among the different variables affecting

thestrength of lime-stabilized clay soil,

curing is of major importance. Its effect on

strength is a function of time, temperature

and relative humidity. The strength increases

rapidly at first, generally during the first7

days of curing, then increases more slowly at

a more or less constant rate.

Page 3 of 7

Journal for Studies in Management and Planning

Available at

http://edupediapublications.org/journals/index.php/JSMaP/

e-ISSN: 2395-0463

Volume 02 Issue 10

October 2016

Available online: http://edupediapublications.org/journals/index.php/JSMaP/ P a g e | 41

F.G.Bell(1996) conducted a series of tests on

different clay deposits containing

mineralsnamely kaolinite, montmorillonite

and quartz . These clay deposits were lime

stabilized in order to address their plasticity,

strength and compressibility problems. Lime

is used as a stabilizing agent in this study.

This investigation revealed that the plasticity

of montmorillonite was reduced whilst that

of kaolinite and quartz was reduced. The

reduction in liquid limit along with the

increase in plastic limit, produced a

considerable reduction in the plasticity index

of montmorillonite. The shrinkage

characteristics of expansive clayey soils are

improved significantly by the addition of

lime.

Sherwood (1993) had explained about the

mechanism of soil lime mix. When lime

isadded to a clay soil it has an immediate

effect on the properties of the soil as cation

exchange begins to take place between the

metallic ions associated with the surfaces of

the clay particles and the calcium ions of the

lime. Clay particles are surrounded by a

diffuse hydrous double layer which is

modified by the ion exchange of calcium.

This alters the density of the electrical charge

around the clay particles which leads to them

being attracted closer to each other to form

flocs, the process being termed flocculation.

It is this process which is primarily

responsible for the modification of the

engineering properties of clay soils when

they are treated with lime.

Hilt and Davidson (1960) proposed that

when lime is added to a clay soil, it must

firstsatisfy the affinity of the soil for lime,

that is, ions are adsorbed by clay minerals

and are not available for pozzolanic reactions

until this affinity is satisfied. Because this

lime is fixed in the soil and is not available

for other reactions, the process has been

referred to as lime fixation. The lime fixation

point corresponds with the point where

further addition of lime does not bring about

further changes in the plastic limit. This

therefore is the optimum addition of lime

needed for maximum modification of the soil

and is normally between 1 and 3% lime

added, by weight. Beyond this point lime is

available to increase the strength of the soil.

Croft (1964) by experimental observation of

28 percent increase in liquid limit ontreating

kaolinite with 2 percent lime, suggested that

such a rise was due to the action of hydroxyl

ions which modified the affinity of the

surfaces of the clay particles for water.

MATERIALS USED

Soil

Locally available black cotton soil is used to

prepare the soft clay. The soil is collected

from the location near the Godavari basin.

The properties of soil are presented in Table

1. All the properties of soil are determined as

per IS 2720-1987

Table 1: Properties of the soil used.

S.No.

PROPER

TY VALUE

1. Gravel 4%

2. Sand 26%

3. Silt 32%