Strength Characteristics and Micropore Structures of Residual Soil with Different Suctions

Abstract

This paper presents micro–macro behaviors of unsaturated residual soils within high suctions. A series of unsaturated soil specimens was prepared using the saturated-saline-solution-based vapor equilibrium technique, considering different initial dry densities. The strength of these specimens was tested under high suction using the direct shear test. Micropore structures for residual soil tests were analyzed using mercury intrusion porosimetry and scanning electron microscopy. The macromechanical strength of residual soil under direct shearing and unconfined compressing conditions was improved by increasing the suctions and densities. And, the level of pore volume distribution measured in microscale on unsaturated residual soil was greatly dependent on matric suction and specimen density. Moreover, soil–water characteristic curves greatly decreased and trended to flat in the high-suction condition (more than 50 MPa).