Compaction of soils required for different types materials for embankment and subgrade are shown here based on IS:2720 – part-8.
Following table shows the relative compaction for different soil types:
Sl. No. | Type of work / material | Relative compaction as percentage of maximum laboratory dry density |
1 | Subgrade and earthen shoulders | Not more than 97 |
2 | Embankment | Not more than 95 |
3 | Expansive clays |
|
a) Subgrade and 500mm portion below subgrade | Not allowed | |
b) Remaining portion of embankment | Not more than 90 |
Selection of compaction rollers for different soil types:
Types of compaction rollers | Suitability of compaction roller for different types of soils | ||
Cohesive soils | Well graded granular and dry cohesive soils | Uniformly graded materials | |
1. Smooth wheeled roller | Suitable | Suitable | Suitable only if the roller is towed by tractors and the load per cm width of the roller is less than 55kg. |
2. Pneumatic | Suitable | Suitable when load on each wheel is more than 2 tonnes | Suitable only if the roller is towed by tractors and load on each wheel is less than 1.5 tonnes |
3. Vibratory roller | Suitable only when the static load per cm width of the vibratory roller is more than 7kg. | Suitable | Suitable but when the static load per cm width of the vibratory roller is more than 12 kg, the roller should be towed by tractors. |
4. Sheep foot roller | Suitable | Unsuitable | Unsuitable |
4. Power rammer | Suitable | Suitable | Unsuitable |
Note: For the purpose of this table, soils are grouped as follows:
1. Cohesive soils include clays upto 20% of gravel and having a moisture content not less than the value of the plastic limit minus 4.
2. Well graded granular and dry cohesive soils include clays containing more than 20% of gravel and / or having a moisture content less than the value of the plastic minus – 4, well graded sands and gravels with a uniformity coefficient exceeding 1- and all shales and clinker ash.
3. Uniformly graded material includes sands and gravels with a uniformity coefficient of 10 or less and all silt and pulverized fuel ashes. Any soil containing 80$ or more of material in the particle size range 0.06 – 0.002 mm will be regarded as silt for this purpose.
Density requirement of embankments and subgrade material:
This requirement of density of soil for embankment and subgrade is based on results obtained when tested as per IS 2720 – (Part – 8).