Hydro-mechanical degradation of granitic saprolites due to capillary imbibition: Laboratory observations and implications for slope failure

Granite saprolite (GS) slope failure is a common yet catastrophic phenomenon in South China. Although the impact of subtropical climate, characterized by high temperatures and heavy rainfall, is widely recognized, the effect of the capillary imbibition and drying (CID) process, which frequently occurs during the dry season, on the hydro-mechanical properties of GS and slope stability is largely overlooked. This research examines natural GS specimens with various degrees of weathering subjected to CID cycles. The study investigates the capillary imbibition (CI) process and the evolution of the soil's hydro-mechanical properties across CID cycles. The results indicate that the CI process in GS is fundamentally different from that in clays and sands. The aggregated structure of GS comprising numerous fissures and large pores plays a critical role. In addition, the CID cycles cause the hydro-mechanical degradation of GS, including a finer particle composition, decreased shear strength, and increased permeability and disintegration potential, where damage to soil cementation and fissure development are identified as critical factors. This investigation reveals new insights into the mechanical properties of GS that are essential for the development of effective landslide management strategies in South China.