Quality Assurance Handbook for Rural Roads Volume-I - pmgsy

Guidelines for carrying out Soil and Materials Survey
69
Quality Assurance Handbook for Rural Roads
Examine any existing information on the geological and soil conditions likely to be met.
Annex 408.1
Along the centre line, have a single line of borings/ test pits made, wherever there is a visible
change in the soil type. If same soil conditions prevail, at least 3 borings/test pits per kilometre
length or a double line offset 15 m to 30 m.
Test pits 1 m x 1 m may be taken to a depth upto 1.5 m, generally the maximum depth of borrow
pits.
Use of hand-operated post hole auger will help.
For a high embankment, boring to be taken to a depth about twice the height of the embankment,
if possibility exists of a soft underlying material.
Get indication of the depth of Ground Water Table(GWT) and its fluctuations.
Note change in vegetation, indicative of subsoil conditions.
Carry out field identification of the local materials by hand-feel tests.
Samples to be collected for classification tests from each boring (generally 2 to 5 kg sample is
enough). Location and depth of strata to be tagged on to the sample bag.
For each soil type or group, a 20 kg sample will be required for compaction and strength (CBR)
tests.
Neighbouring quarries and cuttings should be inspected and representative samples of all
aggregates (soft and hard) collected for laboratory testing.
Besides collecting representative samples of naturally occurring soils, moorums, gravels, soft/
hard aggregates, any industrial wastes and stabilizers like lime from roadside kilns etc. should
also be collected for laboratory testing.