Evaluation of dispersive nature of soil in the piping affected regions of Kerala

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The soil piping erosion has been closely related to the soil composition and its dispersive nature. The phenomenon of dispersivity is explained by the property by virtue of which the soil breaks down into their component particles upon exposure to water. Dispersive soils are highly prone to erosion. If the soil at top is hard and soft dispersive clays present at bottom, in presence of seepage water, there are chances for piping erosion to occur. These kinds of process are very common in lateritic terrains. In appearance the normal erosion resistant clays are similar to dispersive clays, they are, in fact, prone to significant erosion and are susceptible to severe damage. Exchangeable sodium present in the soil is the primary cause of dispersivity. Special methods are required to distinguish between dispersive and non-dispersive soils, common soil classification tests are not sufficient. The recommended tests to identify the dispersive clay soils are Crumb test, Double hydrometer test, Pin hole erosion test, and some chemical tests.This paper reports the problems associated with dispersive soils and discuss the results of double hydrometer tests carried out in various piping regions of Kerala along with the stabilization of dispersive soils with lime. Double hydrometer test as per British standards have been used in the present study. Comparative study of the dispersion ratios obtained for various samples shows that the Idukki samples are having more dispersion ratio than other regions. And as the piping was present in those areas the dispersion ratio was expected to be higher than 30%, the lower values obtained can be due to the erosion of dispersive clays in those regions. Effectiveness of stabilization with lime is checked and it was found that the ideal proportion of lime for minimizing dispersion potential is 1%.