Quality Assurance Handbook for Rural Roads Volume-I - pmgsy

HAND-FEEL TESTS FOR MATERIALS
1. SOILS
1.1 Dilatancy Test
SIMPLE/HANDFEEL TESTS
Quality Assurance Handbook for Rural Roads
APPENDIX - 1
Remove all particles larger than IS 425 micron sieve size and prepare a pat of moist soil with a
volume of about 8000 mm 3 . Make the soil soft by adding water if necessary. Place the pat of soil on
the open palm of one hand and shake horizontally by striking against the other hand, a number of
times. A positive reaction consists of the appearance of water on the surface of the pat rendering
the surface glossy, which disappears when the sample is squeezed between the fingers, the pat
stiffens and begins to crumble. The rapidity of appearance of water during shaking and its
disappearance during squeezing signify the nature of fines in the soil pat. While clean fine sands
give the quickest reaction, a plastic clay shows no reaction at all and silts will show a fairly quick
reaction by way of a shiny surface.
1.2 Dry Strength Test
Remove all particles larger than IS 425 micron sieve size and mould a pat of soil to the consistency
of putty by adding water, if necessary. Dry the pat by air drying or under the sun or in an oven
and test its strength by breaking and crumbling between fingers. The strength of dried pat of soil
is indicative of its plasticity and the nature, as well as quantity of the colloidal fraction. Dry strength
increases with increasing plasticity and is of a very high order in highly swelling type Black Cotton
soils. While the CH soils exhibit high dry strength, the silts and silty fine sands have only slight
dry strength but can be distinguished by the feel when powdering the dried sample: fine sands
feel gritty while silts give a smooth feel.
1.3 Toughness Test
Remove all particles larger than the IS 425 micron sieve size and mould a soil specimen of about
12 mm cube in size, at the consistency of putty. If the soil sample is too dry, adequate amount of
water should be added to bring it to the consistency of putty; if too sticky, allow it to lose some
moisture by evaporation. Roll out the specimen by hand on a smooth surface or between palms
into a thread about 3 mm diameter. The thread should then be folded and re-rolled separately.
During such a manipulation, the thread stiffens, loses its plasticity and crumbles at a moisture
content corresponding to the Plastic Limit. Lump together the pieces of crumbled thread, apply
kneading action until the lump crumbles. Tougher the thread near the Plastic Limit and stiffer the
lump when it finally crumbles, higher the plasticity and more potent is the colloidal clay fraction
in the soil. Weakness of the thread at Plastic Limit and quick loss of cohesion of the lump below
the Plastic Limit signify clay of low plasticity or such materials which occur below the “A”-line in
the Plasticity Chart.
Appendix-1/1