Specification Part 3 - Road & Bridge Works - Urban Administration ...

minimum dry density as given in Table 300-3.
In case where the difference between the sub-grade level (top of the sub-grade on which pavement
rests) and ground level is less than 0.5 m and the ground does not have 98 percent relative compaction
with respect to the dry density (as given in Table 300-3), the ground shall be loosened upto a level 0.5
m below the sub-grade level, watered and compacted in layers in accordance with Clauses 305.3.5 and
305.3.6 to achieve dry density not less than 98 percent relative compaction as given in Table 300-3.
Where so directed by the Engineer, any unsuitable material occurring in the embankment foundation
(500 mm portion just below the sub-grade) shall be removed, suitably disposed and replaced by
approved materials laid in layers to the required degree of compaction.
305.3.5 Spreading material in layers and bringing to appropriate moisture content
305.3.5.1 In construction of embankment/ sub-grade the construction material shall be spread in layers
of uniform thickness not exceeding 200 mm compacted thickness over the entire width of embankment
by mechanical means, finished by a motor grader. It shall be compacted as per Clause 305.3.6.
Successive layers shall not be placed until the layer under construction has been thoroughly compacted
to the specified requirements as in Table 300-3 and got approved by the Engineer-in-charge. Each
compacted layer shall be finished parallel to the final cross-section of the embankment.
305.3.5.2 Prior to commencement of compaction the Moisture content of the material shall be checked
at the site of placement as per IS 2720 Part-2 if found to be out of specified limits, the same shall be
made good. Where water is required to be added in such constructions, water shall be sprinkled by a
water tanker fitted with sprinkler. The water shall be added uniformly and thoroughly mixed in soil by
blading, harrowing until a uniform moisture content is obtained throughout the depth of the layer.
If the moisture content found more than specified limit than it shall be dried by aeration and exposure to
the sun, till the moisture content is acceptable for compaction. Compaction work shall be suspended till
the moisture is accepted for compaction.
Moisture content of each layer of soil shall be checked in accordance with IS: 2720 (Part 2), and unless
otherwise mentioned, shall be so adjusted, making due allowance for evaporation losses, that at the
time of compaction it is in the range of 1 percent above to 2 percent below the optimum moisture
content determined in accordance with IS: 2720 (Part 8) as the case may be. Expansive clays shall,
however, be compacted at moisture content corresponding to the specified dry density, but on the wet
side of the optimum moisture content obtained from the laboratory compaction curve.
Clods or hard lumps of earth shall be broken to have a maximum size of 75 mm when being placed in the
embankment and a maximum size of 50 mm when being placed in the sub-grade.
305.3.6 Compaction: The compaction equipment of suitable size & capacity as approved by the
Engineer-in-charge shall be employed to compaction work. The compaction equipment are static three
wheel roller, self propelled single drum vibratory roller, vibratory tandem roller, pneumatic tyred, pad foot
rollers, etc. The compaction equipments may be used either individually or in suitable combinations.
The Contractor shall demonstrate the efficacy of the equipment he intends to use by carrying out
compaction trials. The procedure to be adopted for these site trials shall first be submitted to the
Engineer-in-charge for approval.
Each layer of the material shall be thoroughly compacted to the densities specified in Table 300-3.
Subsequent layers shall be placed only after the finished layer has been tested according to Clause
903.2.2 and accepted by the Engineer-in-charge.
If density measurements shows reveal any soft areas in the embankment /sub-grade/earthen shoulders
than, further compaction shall be carried out as directed by the Engineer. If inspite of that the specified
compaction is not achieved, the material in the soft areas shall be removed and replaced by approved
material & than compacted using appropriate compactor such as light weight vibratory roller, double
drum walk behind roller, vibratory plate compactor, trench compactor or vibratory tamper to the density
requirements and satisfaction of the Engineer-in-charge.
305.3.7 Drainage: The surface of the embankment/sub-grade at all times during construction shall be