Compaction and Roller Requirement for Embankment and Subgrade

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

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

S. No.

Type of work

Maximum laboratory dry density (unit weight)

1.

Embankments upto 3m height and not subjected to extensive flooding

Not less than 15.2 kN/m³

2.

Embankments exceeding 3m height or embankments of any height subject to long period of inundation

Not less than 16.0 kN/m³ 

3.

Subgrade and earthen shoulders / verges / backfill

Not less than 17.5 kN/m³