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

4 Where the available embankment materials (Soil) are not conducive to plant growth, topsoil
from areas of cutting and areas to be covered by embankment should be stripped to specified depth
not exceeding 150 mm and stored for covering slopes, and other disturbed areas where re-vegetation
is required.
5. If the granular 1 m of the new sub-grade level, the same should be scarified to a depth of at
least 50 mm for achieving bond between old and new material.
6. If the existing surface is of cement concrete type and lies within 1 m of the new sub-grade
level, the same shall be removed completely.
7. The size of the coarse material in the mixture of earth used for embankment construction
should ordinarily not exceed 75 mm.
8 The soil should be spread over the entire width of the embankment in layers not exceeding 200
mm compacted thickness. The clods should be broken to less than 75 mm size & 50 mm for sub grade.
9. Expensive clay exhibiting swell & shrinkage properties shall not be used as fill material.
10 Each layer of sub grade & soulder should be compacted to at least 98 percent and
embankment 97% of the Standard Proctor Density.
11. Ensure that longitudinal and cross profiles should be in conformity with the approved drawings.
12. Approval of the site Engineer should be obtained for each finished layer. Subsequent layers
shall be placed only after the finished layer has been tested and accepted by site Engineer. (Such an
approval would require surface level and compaction control tests).
13 When an existing embankment and/ or sub-grade is to be widened and its slopes are steeper
than 1 vertical to 4 horizontal, continuous horizontal benches, each at least 300 mm wide, should be
cut into the old slope for ensuring adequate bond with the fresh embankment/ sub-grade material to be
added.
14 When the width of the widened portions is insufficient to permit the use of conventional
rollers, compaction shall be carried out with the help of small vibratory rollers/ plate compacters/
power rammers or any other equipment approved by the Engineer.
15 The filling around culverts and bridges, for forming approaches up to a distance of twice
the height of the road from the back of abutment should be done with granular materials and
should not be placed until the concrete or masonry has been in position for 14 days. Approval
for the sequence of work and equipment should be obtained from the Engineer-in-charge before
taking up the work.
16. Control Tests & Frequency
Test
Frequency (min.)
Gradation One test per 200 m 3
Atterberg limits One test per 200 m 3
Moisture content prior to compaction One test per 250 m 3
Density of compacted layer One test per 500 m 3
Deleterious constituentsAs required
C.B.R. As required
17. Discourage borrow pits along the road; where permitted, ridges of minimum 8 m
width should be left at intervals not exceeding 300 m. Small drains should be cut through the
ridges to facilitate drainage.
The depth of borrow pits should be so regulated that their bottom does not cut an imaginary
line having a slope of 1 vertical to 4 horizontal projected from the edge of the final section of the
bank, the maximum depth in any case being limited to 1.0 m.
18. Do maintain a camber/ cross fall of 4 percent during construction for effective drainage