Mini Project on Hydraulic Characterestics of Soils

8/4/2019 Mini Project on Hydraulic Characterestics of Soils

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MINI PROJECT ON

HYDRAULIC CHARACTERESTICS OF SOILS

Project Guide

Dr.

National Institute of Technology, Calicut

WINTER SEMESTER 2010-11MINI PROJECT

Roll No. Name of the Student Branch


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CERTIFICATE

This is to certify that this is a bonafide record of the project presented by the

students, whose names are given below, during Winter Semester 2010-11 in

partial fulfilment of the requirement of the course CEU 398 Mini Project.

Course Coordinator Project Guide

Roll No. Name of the Student Branch


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ACKNOWLEGEMENTS

We would like to thank the following for their kind support and valuable

information provided without whom it would have been impossible to complete

the project successfully.

Dr. Mini Remanan, faculty incharge of Mini Project Course for giving usthis opportunity.

Dr. Kodi Ranga Swamy, faculty guide for the project for his guidance andmoral support.

Mr.Mohanlal, Ms.Shiji , for providing valuable information, help andsupport regarding our project.

GROUP MEMBERS


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CONTENTS

SL.NO CONTENTS PG.NO

1 INTRODUCTION 5

2 OBJECTIVE 6

3 METHODOLOGY 6

4 PRINCIPLES AND THEORIES 7

5 EXPERIMENTAL INVESTIGATIONS 10

6 OBSERVATIONS 29

7 CONCLUSION 31

8 REFERENCE 32


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INTRODUCTION

A material is porous if it contains interstices. The porous material is permeable

if the interstices are interconnected or continuous. A liquid can flow through a

permeable material. Electron photomicrographs of even very fine clays indicate

that the interstices are interconnected. However, the size, cross section and

orientation of the interstices in different soils are highly variable. In general, all

the soils are permeable.

The property of the soil which permits flow of water (or any other liquid)

through it, called the permeability. In other words, the permeability is the ease

with which water can flow through it. A soil is highly pervious when water can

flow through it easily. In an impervious soil, the permeability is very low and

water cannot easily flow through it.

Permeability is a very important engineering property of soils.Knowledge of permeability is essential in a number of soil engineering

problems, such as settlement of buildings, yield of wells, seepage through and

below the earth structures. It controls the hydraulic stability of soil masses. The

permeability of soils is also required in the design of filters used to prevent

piping in hydraulic structures. The permeability of soil also governs the

selection of soil to be used for cores in earth dams and drains in clay. So it

becomes necessary to study on the permeability characteristics of soil.


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OBJECTIVE

To carry out permeability tests on various soils and to determine thecoefficient of permeability.

To study the permeability characteristics of soils at different clay contentsand water contents.

To contribute our results for engineering and planning for structures.

METHODOLOGY

Various soil samples from different areas of NITC are collected. Using sand replacement method, the bulk density of the soil samples was

determined.

Permeability test were conducted on these soil samples by compacting thesoil to the bulk density obtained from the field.

Different soil samples were prepared by varying the clay content and alsoby varying the water content to which the soil is compacted.

Permeability test were conducted on these soil samples.


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PRINCIPLES AND THEORIES

Darcys Law

The flow of free water through the soil is governed by darcys law. Darcy

demonstrated experimentally that for laminar flow in a homogeneous soil, the

velocity of flow (v) is given by,

v = ki

where k = coefficient of permeability, i = hydraulic gradient

the velocity of flow is known as discharge velocity or the superficial velocity.

The discharge q is obtained by multiplying the velocity of flow (v) by the total

cross sectional area of the soil (A) normal to the direction of flow. Thus

q = vA = kiA

The area A includes both the solids and the voids.

Thus the coefficient of permeability is defined as the velocity of flow which

would occur under unit hydraulic gradient.

Determination of coefficient of permeability

The coefficient of permeability of a soil can be determined in the laboratory

using constant head permeability test and variable head permeability test.

1)CONSTANT HEAD PERMEABILITY TESTa) Theory :

The head causing flow is kept constant. Using darcys formula ,the

coefficient of permeability


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k=QL/(Aht)

Q= quantity of water flowing in time t ,cm3

L= length of sample , cm

A= crossectional area of sample, cm2

h = head causing flow cm

t = time interval, s

b) Apparatus :The coefficient of permeability of a relatively more permeable soil can

be determined in a laboratory by the constant head permeability test.

The test is conducted here in an instrument known as JODH PUR

PATTERN PERMEAMETER with accessories . The apparatus

consists of a metallic mould ,having internal diameter 75 mm,

effective height 67mm and a capacity of 296 cc. the mould is provided

with a detachable extension collar of 75 mm internal diameter and 30

mm high ,required during compaction of soil. Mould is provided with

a drainage base plate with a recess for a porous stone. The mould is

fitted with a drainage cap having an inlet valve and an air release

valve, both having fitting for clamping.

c) Preparation of specimen:A known quantity of dry soil is taken with a desired density of

compaction. It is mixed with specified quantity of water and its

thoroughly mixed. The soil is then filled in the permeameter mould

and compacted by static or dynamic compaction.

d) Procedure :The permeameter setup is attach to a constant head reservoir through

the drainage cap. The water is allowed to flow out from the drainage

base for sufficient time such that a steady flow is established. Air at

top of the specimen is removed by opening the air vent. Water is

allowed to flow under constant height. The water collected during a

specified time interval is used to calculate the discharge. The head

causing flow and the temperature of water used for test is noted.


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2)VARIABLE HEAD PERMEABILITY TESTa) Theory :

Head causing flow changes with time. The time needed for change in

head causing flow from h1 to h2 is noted. The coefficient of

permeability is derived using darcys law as

k = 2.303aL log10(h1/h2)/A(t2-t1)

a = area of stand pipe, cm2

L = length of test specimen, cm

A = cross sectional area of the specimen, cm2

t2-t1 = time interval for head to fall from h1 to h2, s

h1, h2 = heads causing flow at the beginning and the end of the interval

of time, cm

The apparatus and the preparation of test specimen are as discussed in

the constant head permeability test.

b) Procedure :A pipe is attached to the drainage cap to allow water flow in. The

water is allowed to flow out from the drainage base for sufficient time

such that a steady flow is established. Air at top of the specimen is

removed by opening the air vent. The inside diameter of the stand pipe

is measured. The time required for water level to fall from initial head

(h1) to a known head (h2) is found. The temperature of water used for

test is noted.


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EXPERIMENTAL INVESTIGATIONS

VARIATION OF PERMEABILITY WITH WATER CONTENT

(CONSTANT HEAD PERMEABILITY TEST)

SAMPLE NO: 1

SOIL IDENTIFICATION: LATERITE SOIL WITH 5% WATER ADDED

TEST NO: 1

DATE: 01/04/2011

OBSERVATIONS

Dimensions of specimen

Diameter: 7.5 cm

Length: 6.7 cm

Area: 44.1786 cm2

Test temperature: 280C

Density to which the soil is compacted: 1.5 g/cc

Volume: 296 cm3

Mass of the soil sample taken : 444g

Viscosity of water at 280C: 8.36 milli poise


Sl no Head (cm) Hydraulicgradient

Time (s) Quantity ofwater (cc)

Kt (cm/s) K20 (cm/s)

1 64.4 9.612 10 38 8.949 x10-3

7.415 x10-3

2 57.3 8.552 10 33 8.734 x10-3

7.236 x10-3

3 48.8 7.283 10 26 8.080 x10-3

6.696 x10-3

Coefficient of permeability Kt = 8.588 x10-3

cm/s

Coefficient of permeability K20= 7.116 x10-3 cm/s


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SAMPLE NO: 2


TEST NO: 1

DATE: 01/04/2011

OBSERVATIONS


Diameter: 7.5 cm

Length: 6.7 cm

Area: 44.1786 cm2



Volume: 296 cm3


Viscosity of water at 28

0

C: 8.36 milli poise


Sl no Head (cm) Hydraulic

gradient

Time (s) Quantity of

water (cc)


1 62 9.254 5 26 12.72 x10-3

10.539 x10-3

2 58.7 8.761 5 19 9.818 x10-3

8.135 x10-3

3 49.9 7.448 5 16 9.726 x10-3

8.058 x10-3


cm/s

Coefficient of permeability K20= 8.911 x10-3

cm/s


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SAMPLE NO: 3

SOIL IDENTIFICATION: LATERITAE SOIL WITH 15% WATER ADDED

TEST NO: 1

DATE: 01/04/2011

OBSERVATIONS


Diameter: 7.5 cm

Length: 6.7 cm

Area: 44.1786 cm2



Volume: 296 cm3




0

C: 10.09 milli poise


gradient


water (cc)


1 63.8 9.522 10 19 4.516 x10-3

3.742 x10-3

2 59.2 8.836 10 17 4.355 x10-3

3.608 x10-3

3 53.3 7.955 10 16 4.553 x10-3

3.772 x10-3


cm/s


cm/s


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SAMPLE NO: 4


TEST NO: 1

DATE: 01/04/2011

OBSERVATIONS


Diameter: 7.5 cm

Length: 6.7 cm

Area: 44.1786 cm2



Volume: 296 cm3




0

C: 10.09 milli poise


gradient


water (cc)


1 62.9 9.388 410 5 2.940 x10-3

2.436 x10-3

2 59 8.806 1037 19 4.709 x10-3

3.902 x10-3

3 51.9 7.746 872 14 4.691 x10-3

3.887 x10-3


cm/s


cm/s


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PERMEABILITY OF SOILS COLLECTED FROM VARIOUS SITES OF

NITC

1) SOIL SAMPLE IN FRONT OF THE GEO TECHNICAL LAB

FIELD DENSITY BY SAND REPLACEMENT METHOD

Calibration for bulk unit weight of sand

Sl no Observations and calculations values

Observations

1 Volume of calibrating cylinder, Vc (cc) 1178.09

2 Weight pouring cylinder filled with sand, W1 (kg) 6.6923 Weight pouring cylinder after pouring sand into the calibrating

container and cone, W3 (kg)

4.730

4 Mean weight of sand in the cone, W2 (kg) 0.364

Calculations

5 Weight of sand in calibrating container, Wc = W1-W3-W2 (kg) 1.598

6 Bulk unit weight of sand, s = Wc/Vc (g/cc) 1.356

Dry unit weight of soil

Sl no Observations and calculations ValuesObservations

1 Weight of excavated wet soil from hole, Wews (kg) 1.190

2 Weight of pouring cylinder filled with sand, W1 (kg) 6.692

3 Weight of pouring cylinder after pouring sand in to the hole and

cone, W4 (kg)

5.354

Calculations

4 Weight of sand in the hole, Wh = W1-W4-W2 (kg) 0.974

5 Volume of sand in the hole, Vh = Wh/s (cc) 718.289

6 Bulk Unit weight of soil, b = Wews/Vh (g/cc) 1.657

Bulk Unit weight of sample soil ,b = 1.657 g/cc


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VARIABLE HEAD PERMEABILITY TEST

SAMPLE NO: 5

SOIL IDENTIFICATION: SOIL SAMPLE IN FRONT OF GEOTECHNICAL LAB

TEST NO: 1

DATE: 24/03/2011

OBSERVATIONS


Diameter: 7.5 cm

Length: 6.7 cm

Area: 44.178 cm2



Volume: 296 cc

Area of stand pipe: 1.7671 cm2

Mass of the soil sample taken : 488.395g



Sl no Initial height

h1 (cm)

final height

h2 (cm)

Head loss

from h1 to h2

(cm)

Time interval

for h1 to h2

(s)

Kt (cm/s)

1 71.8 63 8.8 75 4.673 x10-42 71.8 63 8.8 76 4.611 x10

-4

3 71.8 63 8.8 77 4.552 x10-4

4 71.8 63 8.8 78 4.493 x10-4

5 71.8 63 8.8 78 4.493 x10-4


cm/s

Coefficient of permeability K20= 3.781 x10-4 cm/s


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2) SOIL SAMPLE NEAR ARCHITECTURE BLOCK




Observations


2 Weight pouring cylinder filled with sand, W1 (kg) 6.692

3 Weight pouring cylinder after pouring sand into the calibrating


4.730


Calculations

5 Weight of sand in calibrating container, Wc = W1-W3-W2 (kg) 1.598



Sl no Observations and calculations Values

Observations




cone, W4 (kg)

5.076

Calculations






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SAMPLE NO: 6

SOIL IDENTIFICATION: SOIL SAMPLE NEAR ARCHITECTURE BLOCK

TEST NO: 1

DATE: 24/03/2011

OBSERVATIONS


Diameter: 7.5 cm

Length: 6.7 cm

Area: 44.178 cm2



Volume: 296 cc


Mass of the soil sample taken : 428.30 g




h1 (cm)

final height

h2 (cm)

Head loss

from h1 to h2

(cm)

Time interval

for h1 to h2

(s)

Kt (cm/s)

1 71.8 63 8.8 58 6.043 x10-4

2 71.8 63 8.8 61 5.745 x10-4

3 71.8 63 8.8 66 5.310 x10-4

4 71.8 63 8.8 68 5.154 x10-4

5 71.8 63 8.8 70 5.007 x10-4


cm/s


cm/s


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3) SOIL SAMPLE IN FRONT OF OAT




Observations





4.730


Calculations

5 Weight of sand in calibrating container, Wc

= W1-W

3-W

2(kg) 1.598




Observations




cone, W4 (kg)

5.367

Calculations






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SAMPLE NO: 7

SOIL IDENTIFICATION: SOIL SAMPLE IN FRONT OF OAT

TEST NO: 1

DATE: 24/03/2011

OBSERVATIONS


Diameter: 7.5 cm

Length: 6.7 cm

Area: 44.178 cm2



Volume: 296 cc






h1 (cm)

final height

h2 (cm)

Head loss

from h1 to h2

(cm)

Time interval

for h1 to h2

(s)

Kt (cm/s)

1 71.8 63 8.8 75 4.673 x10-4

2 71.8 63 8.8 75 4.673 x10-4

3 71.8 63 8.8 75 4.673 x10-4

4 71.8 63 8.8 75 4.673 x10-4

5 71.8 63 8.8 75 4.673 x10-4


cm/s


cm/s


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4) SOIL SAMPLE BEHIND NLHC




Observations





4.730


Calculations


= W1-W

3-W

2(kg) 1.598




Observations




cone, W4 (kg)

5.334

Calculations






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SAMPLE NO: 8

SOIL IDENTIFICATION: SOIL SAMPLE BEHIND NLHC

TEST NO: 1

DATE: 24/03/2011

OBSERVATIONS


Diameter: 7.5 cm

Length: 6.7 cm

Area: 44.178 cm2



Volume: 296 cc






h1 (cm)

final height

h2 (cm)

Head loss

from h1 to h2

(cm)

Time interval

for h1 to h2

(s)

Kt (cm/s)

1 71.8 63 8.8 29 1.209 x10-3

2 71.8 63 8.8 30 1.168 x10-3

3 71.8 63 8.8 30 1.168 x10-3

4 71.8 63 8.8 30 1.168 x10-3

5 71.8 63 8.8 30 1.168 x10-3


cm/s


cm/s


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5) SOIL SAMPLE NEAR CHEMICAL BLOCK




Observations





4.730


Calculations


= W1-W

3-W

2(kg) 1.598




Observations




cone, W4 (kg)

5.000

Calculations






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SAMPLE NO: 9

SOIL IDENTIFICATION: SOIL SAMPLE NEAR CHEMICAL BLOCK

TEST NO: 1

DATE: 24/03/2011

OBSERVATIONS


Diameter: 7.5 cm

Length: 6.7 cm

Area: 44.178 cm2



Volume: 296 cc






h1 (cm)

final height

h2 (cm)

Head loss

from h1 to h2

(cm)

Time interval

for h1 to h2

(s)

Kt (cm/s)

1 73.8 56.4 17.4 9 8.008 x10-3

2 73.8 56.4 17.4 9 8.008 x10-3

3 73.8 56.4 17.4 9 8.008 x10-3

4 73.8 56.4 17.4 9 8.008 x10-3

5 73.8 56.4 17.4 9 8.008 x10-3


cm/s


cm/s


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VARIATION OF PERMEABILITY WITH CLAY CONTENT IN THE SOIL


SAMPLE NO: 10

SOIL IDENTIFICATION: PURE LATERITE SOIL + 10% MARINE CLAY ADDED

TEST NO: 1

DATE: 24/03/2011

OBSERVATIONS


Diameter: 7.5 cm

Length: 6.7 cm

Area: 44.178 cm2



Volume: 296 cc


Mass of laterite soil taken: 399.6 g

Mass of marine clay taken: 44.4g



Sl no Initial heighth1 (cm)final heighth2 (cm)

Head lossfrom h1 to h2

(cm)

Time intervalfor h1 to h2

(s)

Kt (cm/s)

1 71.8 63 8.8 17 2.0616x10-3

2 71.8 63 8.8 18 1.9471 x10-3

3 71.8 63 8.8 18 1.9471 x10-3

4 71.8 63 8.8 19 1.8446 x10-3


cm/s


cm/s


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SAMPLE NO: 11


TEST NO: 1

DATE: 24/03/2011

OBSERVATIONS


Diameter: 7.5 cm

Length: 6.7 cm

Area: 44.178 cm2



Volume: 296 cc



Mass of marine clay taken: 66.6 g




h1 (cm)

final height

h2 (cm)

Head loss

from h1 to h2

(cm)

Time interval

for h1 to h2

(s)

Kt (cm/s)

1 71.8 63 8.8 24 1.4603 x10-3

2 71.8 63 8.8 25 1.4019 x10-3

3 71.8 63 8.8 26 1.3480 x10

-3

4 71.8 63 8.8 25 1.4019 x10-3


cm/s


cm/s


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SAMPLE NO: 12

SOIL IDENTIFICATION: PURE LATERITE SOIL + 17.5% MARINE CLAY ADDED

TEST NO: 1

DATE: 24/03/2011

OBSERVATIONS


Diameter: 7.5 cm

Length: 6.7 cm

Area: 44.178 cm2



Volume: 296 cc







h1 (cm)

final height

h2 (cm)

Head loss

from h1 to h2

(cm)

Time interval

for h1 to h2

(s)

Kt (cm/s)

1 71.8 63 8.8 39 8.9866 x10-4

2 71.8 63 8.8 39 8.9866 x10-4

3 71.8 63 8.8 40 8.7619 x10-4

4 71.8 63 8.8 40 8.7619 x10-4


cm/s

Coefficient of permeability K20= 7.352x10-4

cm/s


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SAMPLE NO: 13


TEST NO: 1

DATE: 24/03/2011

OBSERVATIONS


Diameter: 7.5 cm

Length: 6.7 cm

Area: 44.178 cm2



Volume: 296 cc







h1 (cm)

final height

h2 (cm)

Head loss

from h1 to h2

(cm)

Time interval

for h1 to h2

(s)

Kt (cm/s)

1 71.8 63 8.8 63 5.563 x10-4

2 71.8 63 8.8 64 5.476 x10-4

3 71.8 63 8.8 65 5.392 x10

-4

4 71.8 63 8.8 65 5.392x10-4


cm/s


cm/s


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SAMPLE NO: 14


TEST NO: 1

DATE: 24/03/2011

OBSERVATIONS


Diameter: 7.5 cm

Length: 6.7 cm

Area: 44.178 cm2



Volume: 296 cc


Mass of laterite soil taken: 333 g

Mass of marine clay taken: 111 g




h1 (cm)

final height

h2 (cm)

Head loss

from h1 to h2

(cm)

Time interval

for h1 to h2

(s)

Kt (cm/s)

1 71.8 63 8.8 98 3.5763 x10-4

2 71.8 63 8.8 99 3.540 x10-4

3 71.8 63 8.8 98 3.5763 x10

-4

4 71.8 63 8.8 99 3.540 x10-4


cm/s


cm/s


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OBSERVATIONS

0

1

2

3

4

5

6

7

8

9

10

0 5 10 15 20 25

permeability

x10-3

cm/s

water content %

permeabilty vs water content

0

5

10

15

20

25

0 5 10 15 20 25 30

permeabilit

yx10-4

cm/s

clay content %

permeability vs clay content


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From the graph between permeability and water content, it was observed that

there is an initial increase in permeability when water content increases and

reaches a maximum and then the permeability is decreased with further increasein water content. When water content was increased beyond 20% the

permeability of the soil was found to be very low.

From the graph between permeability and clay content, it was observed that the

permeability go on decreasing with increase in clay content. The decrease in

permeability was found to be very rapid when the clay content was increased

beyond 20%.

Soil samples collected from various sites of NITC has the coefficient of

permeability values in the range 10-3

to 10-4

cm/s. From the typical coefficient

of permeability values, it can be seen that these soil belongs to fine sand and

loose silts having fair drainage properties.


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CONCLUSION

Coefficient of permeability with water content :The value of the coefficient of permeability is maximum at around 10%

for the laterite soil taken. The coefficient of permeability of the soil

increases with increase in water content, for a water content below 10%

and for above 10% it decreases. The reason for increase in permeability

with increase in water content upto 10% is that the air voids in soil are

filled with water and thus the degree of saturation of soil is increased. At

around 10% water content the soil is fully saturated and hence maximum

permeability is obtained. When water content is increased about 10 % the

flocculated structure of soil is changed to dispersed structure. Hence the

water cant easily flow through the soil. Coefficient of permeability with clay content:

As expected , when the clay content in the soil is increased the coefficient

of permeability of the soil is decreased. Clay being highly cohesive and

having very fine particles, it wont allow the water molecules to pass

through the soil easily. When the amount of bulky, cohesionless particles

is large compared with that of fine grained clayey particles, the bulky

grains are in particle-to-particle contact. The space between the bulky

grains is occupied by the clayey particles making soil less permeable.

Soil sample collected from various sites of nitc was analysed, there wasno much difference in the soil type but the density of the soil was

different in different area. The values of the coefficient of permeability

obtained for the soils was also varying in an irregular manner. So we

concluded that the coefficient of permeability not only depend upon

density but also other factors like soil structure, water content, void ratio,

particle size etc.By comparing the coefficient of permeability values obtained, the soilcollected near chemical block having high value 6.635 x10-3 cm/s and the

soil collected in front of geotechnical lab is having low 3.781 x10-4 cm/s.

From this observation we can conclude that the soil infront of

geotechnical lab is less pervious than the soil collected near chemical

block.


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REFERENCE

DR. K.R.ARORA., SOIL MECHANICS AND FOUNDATION ENGINEERING, (2008)

CASAGRANDE A., CLSSIFICATION AND IDENTIFICATION OF SOILS, VOL 113,

WWW.WIKIPEDIA.ORG

Documents

Mini Project on Hydraulic Characterestics of Soils