Study on swelling and shrinkage behaviour of unsaturated soils from material characteristics

Structural stability of the pavements is affected by shrinkage and swelling behaviour of expansive soil. Thus, determination of swelling (viz., Free swell index, swelling potential and swelling pressure) and shrinkage (viz., shrinkage strain) properties becomes essential. However, swelling and shrinkage properties of expansive soil are affected by rapid moisture variations during drying and wetting process. This paper embraces a practical approach to characterise the moisture distribution during drying. Laboratory testing procedure involves the measurement of drying diffusion coefficients, suction and humidity isotherms on five different clayey soil samples. Non-linear diffusion theory was used for measuring drying diffusion coefficients. Attempts were made to study the swelling and shrinkage behaviour for varying initial water content, dry density, suction and diffusion coefficient. Further, clay mineral identification and characterisation of mineralogical properties are done from X-ray diffraction patterns, cation exchange capacity and specific surface values. Details of the methodologies adopted for theoretical modelling and experimental investigations are presented and results obtained for the present study have been critically evaluated with available literature.