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 %