Objective
1. To
establish the relation between water content and dry density of a soil.
2. To
determine the moisture content for the given soil.
3. To
determine the maximum dry density for the given soil.
Theory
Compaction is necessary process
of exclusion of air under dynamic load, when water is added initially and soil
is compacted. Soil particles move closer, reducing the voids and removing air
from the voids. The process increase the density of soil continuous water acts
like a lubricating agent. Air is reduced and water film is formed around each
particle. Thickness of water film increases with addition of water but it is
not possible to remove air completely. A stage reaches where addition of water
causes replacement of soil particles by water and density of soil decreases
even after compaction.
Apparatus
1. Cylindrical
metal mould with a detachable base plate and a removable coller.
2. Metal
hammer of mass 2.6 kg and drop of 310 mm.
3. Sample
of extruder.
4. Balances
10 kg capacity sensitive to 1 gm and other of capacity 20 gm sensitive to 0.01
gm.
5. Oven,
moisture cans, sieve 19 mm and 4.75 mm, mixing pan, trowel, spatula.
Diagram
Cylindrical metal mould with detachable collar
and base plate
Procedure
Preparation
of specimen
1.
Take 16 kg of air dried soil sample passing
through 19 mm I.S. Sieve.
2. Add water to bring water content to about 10
percent less than the estimated optimum water content.
3. Keep the soil in air tight tin for about 20 hour
to ensure through mixing of the water with the soil.
4. Divide the sample in eight equal parts.
Compaction
test procedure
1. Clean
and empty mould, dry and weigh it to the nearest gram.
2. Apply
grease to the inside of the mould , top of base plate and inside of coller.
3. Fit the
base plate and coller to the mould and place the assembly on the floor.
4. Take
one part of the soil and fill the mould with three equal layers and give as
blocks to each layer from the hammer having mass 2.6 kg dropping from a height
of 310 mm.
5. Scratch
with a spatula every compacted layer before putting the soil for the succeeding
layer.
6. Remove
the coller and trim the compacted soil, level with the top of the mould by
means of straight edga.
7. Weight
the mould with the soil again to the nearest one gram.
8. Eject
the soil from mould bye extruder.
9. Cut the
soil sample in the middle and take representative soil specimen in airtight
container from the middle of cut surface.
10. Determine the moisture content of this
representative sample.
11. Repeat
steps 1 to 10 taking fresh soil sample (from step 10) 5 to 6 times using
additional 60 ml water (3 % of dry soil) than the proceeding specimen.
12.Calculate
the bulk density of the compacted soil for each test.
13.Calculate
corresponding dry densities knowing bulk density and water content for each
test.
14.Draw a
curve showing relationship between moisture content and dry density.
15. Find
out dry density corresponding to the maximum point of the curve and
corresponding moisture content. This dry density is known as maximum dry
density and the moisture content.
Precaution
1. Clean
the mould, base plate and collar at the end of each reading and apply grease
inside the mould, top base plate and inside collar before use for the next
test.
2. See
that blocks of hammer are uniformly distributed on the top of the soil
specimen.
3. The
hammer should not strike the collar while giving blows.
4. Wastage
of soil should be avoided.
5. Fill
mould with loose soil half the height of the mould and compacted the first
layer. For second layer fill the mould to its full height with loose soil and
then compacted for the third layer fill the soil half of collar height and then
compacted it.
6. For
every blows ensure that the height of full of hammer is 310 mm. for light
compaction and 450 mm for heavy compaction.
7. The
last layer after compaction should not provide more than 5 mm above top of the
mould.
Observation
Density
Determination no.
|
1 sample
12 %
|
2 sample
15 %
|
3 sample
18 %
|
4 sample
21 %
|
||||
Mass of mould + compacted
soil in gm (w)
|
6310
|
6370
|
6240
|
6297.5
|
||||
Mass of empty mould in gm (wm)
|
4165 gm
|
|||||||
Mass of compacted soil in gm
|
2145
|
2205
|
2105
|
2075
|
2132.5
|
|||
Mass of dry soil in gm
|
47
|
52
|
27
|
17
|
35.75
|
|||
Bulk density rm = w – wm
/ vm
|
2.02
|
2.264
|
2.161
|
2.130
|
2.189
|
|||
Moisture content (w) percent
|
6.66 %
|
6.25 %
|
9.09 %
|
11.11%
|
3.27 %
|
|||
Dry density gm/ml Yd = Ym / 1+w
|
0.287
|
0.132
|
0.214
|
0.175
|
0.247
|
|||
Container no.
|
A
|
B
|
C
|
D
|
||||
Mass of container + wet
soiling
|
75
|
80
|
55
|
60
|
||||
Mass of container + dry soil
in gm
|
70
|
75
|
50
|
56
|
||||
Mass of water in gm
|
5 gm
|
5 gm
|
5 gm
|
5 gm
|
||||
Mass of container in gm
|
23 gm
|
23 gm
|
23 gm
|
23 gm
|
||||
Moisture content (w) percent
|
6.66 %
|
6.25 %
|
9.09 %
|
9.35 %
|
||||
Graph
Result
1. The
maximum dry density for the soil sample test = 2.13 gm/ml
2. Optimum
moisture content = 15 %
