Quality Assurance Handbook for Rural Roads Volume-I - pmgsy

1300: PROTECTION WORKS AND DRAINAGE
A. Methodology
General
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Quality Assurance Handbook for Rural Roads
In this section, the construction and quality control aspects of aprons, pitching on slopes, masonry
flooring over cement concrete bedding, curtain wall besides chute, roadside and hill drains have been
dealt with.
A-1 Apron
1. Keep the length of apron not less than twice the depth of curtain wall.
2. Level the surface on which the apron is to be laid and prepare for the length and width as shown
on drawings. In case the surface is below low water level, raise the ground level by dumping
earth, moorum, brick bats, stones, etc., so that apron can be laid thereon.
3. Provide flexible apron beyond curtain walls for a minimum distance of 3 m on upstream side and
6 m on downstream side unless specified otherwise.
4. For regular and orderly disposition of stone in apron, build template cross walls in dry masonry,
of about 1 m thickness and full height specified at 30 m intervals all along the length. Hand pack
stone within these walls.
5. Use wire crates of galvanized steel wire of 4 mm dia with apertures not less than 150 mm.
6. Use insitu built wire-crates of size 2 m x 1 m x 0.3 m to 7.5 m x 3 m x 0.6 m and securely stay at 1.5
m intervals or less.
7. Place the crates in position before filling in boulders.
A-2 Pitching on Slopes
1. Use quarry stone of minimum 225 mm thickness or 30 kg as pitching or as specified, and spalls of
minimum 25 mm size to fill the voids. Alternatively PCC blocks of 190 x 190 x 225 mm size
(minimum) in M15 Concrete can be used for pitching.
2. Provide one or two layers of graded materials (filter medium) of 150 mm thick or as specified
under the pitching to drain off the seepage water and prevent erosion of base material.
3. Trim the sides of banks to the required slope and provide before laying the pitching. Fill the
depressions and thoroughly compact before hand.
4. Start the lowest course of pitching from the toe wall and build courses upwards. Use either dry
rubble or brick masonry for toe wall.
5. Use dry masonry, when two or more layers of stones are to be laid to obtain design thickness of
pitching and bond the stones well. Template cross walls in dry masonry can be built, as done for
aprons.
6. When bricks are to be laid in more than one layer, ensure proper bonding the adjacent layers by
means of sufficient number of pin headers extending from one layer to the other.