Quality Assurance Handbook for Rural Roads Volume-I - pmgsy

301. EMBANKMENT CONSTRUCTION
A Methodology
23
Quality Assurance Handbook for Rural Roads
1 Obtain materials (soil) for embankment from approved sources. Preference should be given to
materials that are suitable and become available from nearby road excavation. (Refer Section B for
quality control requirements).
2 After clearing the site, mark the limits of embankment by fixing batter pegs and marking toe lines
on both sides at regular intervals as guides. The embankment shall be built sufficiently wider
(about 300 mm on either side of Roadway) than the specified formation width so that surplus
material at the edges may be trimmed to ensure proper compaction of the edges and side slopes.
3 Remove stagnant water, if any, from the foundation of the embankment.
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 After removing the top soil/ unsuitable material, foundation for embankment construction shall
be prepared as follows:
(a) For embankment less than 1.0 m high over natural ground, the ground surface should be
loosened up to a minimum depth of 150 mm by ploughing or scarifying and compacted to
the specified density as per Para B5.
(b) For embankment less than 0.5 m height over an existing black-topped or gravel road, the
black-topping shall be removed and the pavement/ gravel road should be scarified to a
minimum depth of 150 mm. All particles shall be reduced to a maximum size of 75 mm and
compacted according to Para B5.
(c) If the granular/ black topped surface lies within 0.50 m - 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.
(d) 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.
(e) For embankment over ground not capable of supporting equipment, successive loads of
embankment materials should be spread in a uniformly distributed layer of adequate
thickness to support the equipment and to construct the lower portion of the embankment.
(f) For embankment construction on existing slope steeper than 1 Vertical: 4 Horizontal,
horizontal benches should be cut in the existing slope to a sufficient width to accommodate
placement and compaction equipment.
6 The size of the coarse material in the mixture of earth used for embankment construction should
ordinarily not exceed 75 mm.
7 The soil should be spread over the entire width of the embankment in layers not exceeding 150
mm compacted thickness. The clods should be broken to less than 75 mm size. Each layer at a
moisture content within (±) 2 % of the optimum moisture content, should be thoroughly compacted