Quality Assurance Handbook for Rural Roads Volume-I - pmgsy

302. EARTHWORK IN CUTTING
A. Methodology
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Quality Assurance Handbook for Rural Roads
1. After site clearance, the limits of excavation should be set out true to lines, curves, slopes, grades
and cross-sections as shown on the drawings by constructing reference pillars, back cutting lines,
reference lines (1.5 m away from formation lines on hill and valley sides)
2. If directed, the top soil shall be stripped to specified depths and stockpiled for reuse, as detailed in
sub-section 301.
3. Excavation shall be done manually or mechanically using dozers. After excavation, the sides of
excavated area should be trimmed and the area contoured to minimise erosion and ponding,
allowing natural drainage to take place.
4. Cross drainage works like scuppers or small culverts 1 to 2 m span and side drains, shall be so
constructed along the formation cutting work, as to have least interference with the existing
drainage.
5. The cut formation, which will serve as sub-grade, should be checked for its field density and if the
field dry density of the material in the top 300 mm portion is less than 100 per cent of maximum
Proctor density, the formation material shall be loosened to a depth of 500 mm and compacted in
layers to 100 per cent Standard Proctor Density (IS:2720-Part 7).
6. In hilly areas, cutting should be done from top to bottom. Special attention should also be paid to
side slopes and side drains in cutting.
7. Rock when encountered in road excavation shall be removed upto the formation level. Where
unstable shales or other unsuitable materials are encountered at the formation level, these shall be
excavated to the extent of 500 mm below the formation level.
8. In rocky formation, the surface irregularities shall be corrected with granular base material to
achieve the specified profile and levels.
9. Where blasting is involved for rock cutting, guidelines given in sub-section 304 shall be followed.
10. Excavation in marshes shall begin at one end and proceed in one direction across the entire marsh
immediately ahead of backfilling to ensure complete removal or displacement of muck.
11. For widening of existing pavement, the existing shoulders shall be removed to their full width
and upto sub-grade level to enable proper compaction in the widened portions.
B. Quality Control Requirements
1. Horizontal Alignment
The horizontal alignment should be reckoned with respect to the centre line of the carriageway as
shown on the drawings. The edges of the roadway as constructed should be correct within a
tolerance limit of (±) 30 mm in plain and rolling terrain and (±) 50 mm in hilly terrain.
2. Finishing
No point on the slopes shall vary from the designated slopes by more than 150 mm measured at
right angles to the slope (300 mm in case of rock excavation).