Physico-chemical effect on compressibility of tropical soils

Abstract

The paper examines the role of physico-chemical factors in the consistency limits and compressibility behavior of kaolinitic soils and montmorillonitic soils of residual origin. The liquid limit, equilibrium void ratio at a given load (in the oedometer test) and compression index values of the kaolinitic soils in the remolded state correlate well with the shrinkage limit values, which in turn are a function of the clay fabric. The corresponding engineering properties of the remolded montmorillonitic soils correlate well with the exchangeable sodium content that reflects a soil's potential to develop diffuse ion layer. Oedometer tests with undisturbed samples highlight the role of clay mineralogy in the engineering behavior of residual soils; on inundation with water under a nominal pressure, the kaolinitic soils exhibit no volume change while the montmorillonitic soils exhibit a notable swell. Oedometer tests with undisturbed samples also showed that besides the physico-chemical factors, the in-situ moisture content, density and degree of saturation have an important bearing on the void ratio sustained by the soils at a given stress level.