SOIL

MECHANICS

PROJECT

MECHANICAL

STABILISATION OF

SOIL

PROJECT DESCRIPTION

We are doing the mechanical stabilization of soil. For

this we have decided to do the compaction test. In

compaction we will determine the saturation at which

the max. dry density can be reached in the lab in a

practical scenario.

We know from phase relation that dry density is a

function of G, ρ, S, w. Therefore, if we are to plot

saturation curves for different dry densities we fist have

to determine the value of G.

Therefore, we have the following three main

objectives.

1. We first determine the relative density of soil

solids by the pyconometer method, thus we get

the value of G.

2. Next we perform the compaction test and draw

the compaction curve for different water content

by taking ‘w’ on the x-axis and dry density on the

y-axis.

3. Once we have obtained the compaction curve we

plot the 100% saturation line, we also plot 90%

and 80% saturation lines and so on to see at what

% saturation the soil attains maximum dry density

practically in the lab.

METHODOLOGY OF PROJECT

The following steps are carried out in order to

carry out the project.

1) About 6 to 7 kg of soil is taken from the field and

put into a hot air oven maintained at (105-110 )°C

for at least 24 hours.

2) The moisture less soil is passed through is passed

through a 4.75mm sieve and collected in a steel

plate. The weight of the tray before and after the

addition of soil is noted.

3) Exactly three kgs of soil is separated for the

compaction test(explained later).

4) From the remaining soil the pyconometer test for

determination of relative density is carried out.

PROCEDURE

First we notice that the soil sample that

we have selected is coarse grained soil

since more than 50% of the soil passing

through the 4.75 mm sieve is retained on

the 0.075 mm sieve. Therefore, we carry

out the proctor test as follows :

STANDARD PROCTOR TEST

The compaction test going to be done is the

standard proctor test.

This test has been devoloped by R.R.Proctor in

1933 and is named after him.

This method describes the procedure for

determining the relationship between the moisture

and density of fine-grained or coarse-grained soils.

Equipment Required

A cylindrical metal mould with a nominal capacity

of 944 cm³ and internal diameter of 100 mm and a

height of 127.3 mm.

Rammer: A metal rammer having a 50 mm

diameter circular face with a 2.7 kg weight which

will drop freely for a distance of 310mm.

Straight-edge: A steel straight-edge approximately

300 mm in length.

Oil and oil brush : This is required for lubricating

the ends of the mold where the collar and base

plate are fixed. It is also applied along the insides

of the curved surface of the mold so that the soil

does not stick to its surface.

Electronic weighing machine : This is required to

weigh the mold with and without the soil.

Shovel : This is required to help in mixing the

water in the soil to attain a desired water content.

METHODOLOGY

Since the soil we have selected is coarse grained

therefore we begin the compaction with 4% water

content. It should be remembered that the initial

water content should be a lot lower than the

optimum water content.

The soil is mixed thoroughly with a shovel or by

hand and is divided into three equal parts.

The mold is lubricated with oil and fixed to the

base plate and the collar is attached to the mold.

o Each third is put into the mould with the shovel and rammed

with 25 blows of the rammer evenly distributed over the

mold.

o The same procedure is repeated for the remaining thirds of

the soil sample with the rammer.

o The collar of the mold is removed and the excess soil is

removed with a straight edge. The top surface of the mold is

smoothened.

o Next the mold is weighed to the nearest .5 gm

o The procedure as above is repeated for different water

contents by increasing the water content by 2 % each time.

Readings and Tabulation

Sample.No. 1 2 3

Wt. of empty mold (W1)

Wt. of mold + soil (W2)

Wt. of soil in the mold (W3)

Bulk Density g/c.c (ρ)

Water content, w%

Dry density ρ/(1+w)

Dry weight can be determined from the above

table

A graph is plotted by taking dry density (ρd) on

y-axis and water content (w) on x-axis.

Wt. of the

mould

(w1)

Wt. of

mould+

soil

(w2)

Wt. of soil

(w3)

w3= w2-

w1

Bulk

density

ρ =

W3/V

Water

content

W%

Dry density

ρd=ρ/1+w

4727.5 6505 1777.5 1.882 4 1.8096

4727.5 6716 1988.5 2.106 6 1.9867

4727.5 6864.5 2137 2.263 8 2.0953

4727.5 6896.5 2169 2.297 10 2.0881

4727.5 6862 2134.5 2.261 12 2.0188

Volume of the mould = 944ml

*Weights are in grams

1.75

1.8

1.85

1.9

1.95

2

2.05

2.1

2.15

0 5 10 15

Water Content (W%)

Dry

De

nsi

ty (ρ

d)

DETERMINATION OF RELATIVE

DENSITY OF SOIL SOLIDS.

After the compaction test is over we determine the relative

density of Soil solids by pyconometer method . In this

method we follow the following methodology:

o The weight of the empty pyconometer is taken (W1).

o Next about 200 grams of soil passing through the 4.75

mm sieve is taken and its weight is recorded (W2).

o Water is added to the pyconometer till the soil sample is

completely submerged in water and pyconometer is left

undisturbed for about half an hour.

o After this water is completely filled to the brim of the

pyconometer and its weighed is recorded (W3).

o The instrument is then emptied of the soil sample and

filled with distilled water and its weight is taken(W4).

o The Specific Gravity ‘G’ of the soil is then calculated

according to the formula.

G=(𝒘𝟐−𝒘𝟏)

𝒘𝟐−𝒘𝟏 −(𝒘𝟑−𝒘𝟒)

1 2 3

Wt. of empty

pyconometer (w1)

595 595 595

Wt. of

pyconometer+soil

(w2)

844.5 793.5 798.5

Wt. of

pyconometer+soil

+water (w3)

1637.5 1603.5 1607.5

Wt. of

pyconometer +

distilled water (w4)

1492.5 1492.5 1492.5

*Weights are in grams

SPECIFIC GRAVITY DETERMINATION

SPECIFIC GRAVITY (G) = 2.313

o Next, the graph for the dry density and the water content

is plotted by taking water content on the x-axis and dry

density on the y-axis.

o On this graph, we plot the saturation lines corresponding

to 100% saturation, 90%, 80% and so on and so forth till

a saturation line coincides with the maximum dry density

of the soil. This gives us the maximum achievable dry

density and saturation in an ordinary practical laboratory

session.

SCHEDULE OF WORK

Work to be Done Status

1). Collection of soil sample from

field and submission in lab.

Completed.

2). Performing the compaction

test and noting the values.

Completed.

3). Performing the relative density

test and noting the values.

Completed.

4). Plotting of the graph involving

dry density, water content and

saturation.

Completed.

5). Compilation of final report on

the project and drawing

inferences from the graph.

Pending.