Structural Characterization of Residual Soil and the Effect of Drying and Wetting Cycles on Its Strength

A series of indoor tests was performed to obtain the physical and mechanical properties and structural characterization of granite residual soil. Experimental results indicated that clot and flocculation are the primary forms of microstructure, and the residual appearance of the parent rock’s crystal pattern is reserved. Structural strength is provided by strong cementation and residual chemical bond force. The clay mineral is mostly kaolin, which exhibits a laminated structure. The grain particle of granite residual soil presents the mixed features of sand and clay. The coefficient of compressibility is mostly distributed with in the range of 0.30–0.35 MPa−1, which is for medium compressible soil. Granite residual soil demonstrates good mechanical performance even under saturation condition. However, strength variability is notable. Drying and wetting cycles reduce the strength of granite residual soil, and strength decreases by approximately 30% after two drying and wetting cycles.