Study on swelling and shrinkage behaviour of unsaturated soil

Abstract

ABSTRACT newlineStructural stability of the pavements is affected by shrinkage and swelling behavior of expansive soil. Moisture variations during wetting and drying process affects the shrinkage and swelling characteristics of unsaturated soil. Thus, determination of swelling (viz., Free swell index, swelling potential and swelling pressure) and shrinkage (viz., shrinkage strain) properties becomes essential to ensure the stability. It is important to study the complex behavior of unsaturated soil during drying process. This study embraces a practical approach to characterize the moisture distribution during drying. Characterization of suction with moisture distribution during drying process of unsaturated soil is critical in predicting swelling and shrinkage. However, swelling potential is influenced by initial dry density, initial water content and suction. 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. The soil-water characteristic curve was determined from the measured suction, air-entry value is obtained from this curve. Attempts were made to study the swelling and shrinkage behavior for varying initial water content, dry density, suction and diffusion coefficient. Further, clay mineral identification and characterization 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. The results indicated that moisture loss and strains produced during drying process are independent of initial dry density. At water contents above shrinkage limit, strong influence of water content on shrinkage of soil specimen was observed. In contrast to shrinkage behavior, sw