Effects of Drying-Wetting Cycles on the Mechanical Behavior of Reconstituted Granite-Residual Soils

Abstract

In Central South of China, granite residual soil (GRS) is one of the main subgrade soils for transportation infrastructures. To further understand the effects of drying and wetting (D-W) cycles on the mechanical responses of GRS, this paper presents a series of experimental tests on the microscopic characteristics and mechanical behaviors of reconstituted GRS under different D-W cycles (0, 1, 2, 4). The particle size distribution curve of GRS exhibited an evident unimodal peak. However, the unimodal distribution gradually transformed into a bimodal form with an increase of D-W cycles. A novel designed consolidation apparatus equipped with paired bender elements in three orthogonal directions is developed to investigate the compression behavior and small-strain stiffness of reconstituted GRS. Test results show that the GRS exhibited complicated compression behaviors in response to the cyclic D-Ws. The preconsolidation stress reached a maximum value at the end of the 2nd cycle and then decreased with the subsequent D-W cycles. Cyclic D-Ws resulted in a drastic increase in the small-strain stiffness, and the beneficial effect was more pronounced in the 1st cycle. Stress-induced fabric anisotropy occurred during the compression test. Both the stiffness and stiffness anisotropy increased with increased loading. In the triaxial shearing test, the volume change of the GRS was characterized by coupling effects between the suction history and confining pressure.