Prof. D. N. Singh

SUDARSHAN B. SHINDE

M.Tech.
Indian Institute of Technology Bombay, Powai, India sudarshan1784@gmail.com

SOME INVESTIGATIONS ON CRACKING CHARACTERISTICS OF FINE-GRAINED SOILS

Cracking characteristics of fine-grained soils depend on their physico-chemico-mineralogical properties. As such, this phenomenon can be attributed to the high surface area of the grains and/or the presence of clay minerals (viz., Montmorillonite, Bentonite) or both, and the tensile strength of the soil. Several experimental techniques have been developed by earlier researchers to study cracking characteristics of the fine-grained soils in their bulk form, by resorting to triaxial tests, direct tensile tests or suction measurements. However, most of these studies yield results that are soil specific and dependent on the methodology adopted by the researchers. Apart from this, due to the bulk form of the sample, the sample heterogeneity (i.e., both in terms of the density and moisture content) influences the test results to a great extent. Under this situation, and in the absence of guidelines regarding sample thickness, determination of the cracking characteristics of the fine-grained soils by employing their thin samples (1mm to 5 mm) appears to be an excellent alternative. The genesis of this concept is based on the fact that several such thin layers of the soil would contribute to the cracking characteristics of the soil mass.
With this in view, efforts were made to determine tensile strength of the fine-grained soils by (a) measuring the deflection undergone by a silicone wafer due to air-drying of a thin film of the fine-grained soil with the help of a laser beam and (b) measuring the suction by employing a dewpoint potentiometer, WP4. Results obtained from these tests were critically evaluated vis-?-vis those obtained from the triaxial tests and the empirical relationships reported in the literature. It has been observed that there is a unique relationship between the results of the thin and thick samples. In addition, attempts were made to study the cracking patterns of thin and thick samples of the soils.