TITLE:
TO DETERMINE THE OPTIMUM WATER CONTENT FOR A SOIL UNDER A GIVEN COMPACTION
OBJECTIVES:
To determine the optimal water content at which the soil sample can reach its maximum dry density.
To discuss the relevance of the result of the experiment in civil engineering practice and to compare it with others soil that exhibit different compaction property.
THEORY:
Compaction is any process by which the soil particle at artificially rearranged and packed together into a closure state of contact by any mechanical means so that the dry density of the soil is increased.
Standard proctor test is a laboratory test that can be used to determine the OMC for a soil under given compaction. This test was developed by RR Proctor to provide the relationship between the water content and the dry density of soil.
Bulk mass density, `rho=M/V`
Dry density,`gamma_d=rho/(1+w)`
The wa....Show More
TITLE:
TO DETERMINE THE OPTIMUM WATER CONTENT FOR A SOIL UNDER A GIVEN COMPACTION
OBJECTIVES:
To determine the optimal water content at which the soil sample can reach its maximum dry density.
To discuss the relevance of the result of the experiment in civil engineering practice and to compare it with others soil that exhibit different compaction property.
THEORY:
Compaction is any process by which the soil particle at artificially rearranged and packed together into a closure state of contact by any mechanical means so that the dry density of the soil is increased.
Standard proctor test is a laboratory test that can be used to determine the OMC for a soil under given compaction. This test was developed by RR Proctor to provide the relationship between the water content and the dry density of soil.
Bulk mass density, `rho=M/V`
Dry density,`gamma_d=rho/(1+w)`
The water content corresponding to the maximum dry density is known as optimum moisture content.
For a given water content, theoretical maximum density is obtained corresponding to the condition when there are no air voids.
APPARATUS REQUIRED:
PROCEDURES:
About 3 kg of air-dried pulverized soil sample passing through 4.75 mm sieve is taken. Water is added to the soil to bring its water content to about 4% if the soil is coarse grained and to about 8% if the soil is fine grained. The water content should be much less than the expected optimum water content. The soil is mixed throughly and covered without cloth and left for measuring for about 10 to 15 minutes.
The mass of empty mould with base plate but without collar is taken. The mould is placed on a solid base and filled with soil to about one third of its height. The soil is then compacted by 25 number of blows. The soil surface is scratched with spatula before the second layer is placed and compacted. The mould is filled to about two third height and compacted again by 25 blows. Likewise, the third layer is placed and compacted. The third layer should project about the top of the mould into the collar by not more than 6 mm.
The collar is rotated to break the bond between the soil in the mould and that in the collar. The collar is then removed, and the soil is trimmed off flush with the top of the mould. The mass of the mould,base plate,and the compacted soil is taken, and thus the mass of compacted soil is determined.
OBSERVATIONS:
`Mass\ of\ mou\ld + base\ plate=3.8209\ kg`
`Internal\ diameter\ of\ the\ mou\ld=100\ mm`
`Height\ of\ mou\ld=127.3\ mm`
Table for the calculation of Moisture content:
Trial | Mass of container kg | Mass of container + soil sample | Container Number | Mass of container + dry soil sample |
1 | 0.013 | 0.042 | 55 | 0.0382 |
2 | 0.0113 | 0.054 | 17 | 0.0467 |
3 | 0.0112 | 0.050 | 58 | 0.0430 |
Table for mass of soil sample inside mould in each trial:
Trial | Mass of mould + soil | Container Number | Water content |
1 | 5.580 | 55 | 14% |
2 | 5.8313 | 17 | 17% |
3 | 5.7824 | 58 | 20% |
CALCULATIONS:
`volume=(pid^2)/4*h`
`=(pi*0.1^2)/4*0.1273`
`=0.000999\ m^3`
For container number 55,
density is,` rho_(t1)=M/V`
`=(0.042-0.013)/0.000999`
`=29.005(kg)/m^3 `
Dry density is,`rho_(d1)=rho_(t1)/(1+w)=29.005/(1+0.14) `
`=25.44\ (kg)/m^3 `
For container number 17,
density is,`rho_(t2)=M/V=(0.054-0.0113)/0.000999=42.708\ (kg)/m^3 `
Dry density is,` rho_(d2)= rho_(t2)/(1+w)`
`=42.708/(1+0.17)`
`=36.50\ (kg)/m^3 `
For container number 58,
density is,`rho_(t3)=M/V=(0.050-0.0112)/0.000999=38.807\ (kg)/m^3 `
Dry density is,`rho_(d3)=rho_(t3)/(1+w)=38.807/(1+0.20)=32.34\ (kg)/m^3 `
RESULTS:
Thus, the optimum moisture content for a given soil sample was found to be `16.6%`
SOURCE OF ERRORS:
There may be slight error while observing weight.
The compaction may not be uniform.
The graph may not be plotted accurately.
PRECAUTIONS:
Weight observations should be taken carefully.
The rammer should be allowed to fall freely under gravity during compaction.
The blows should be distributed evenly over the surface.
CONCLUSIONS:
Thus the optimum moisture content for a given soil sample was found out. This value can be of great use in construction using the test sample if maximum compaction is wanted in order to support the maximum possible load.
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