LAUSR

Abstract Slope failures caused by rainfall are common occurrences in many parts of the world and are severe in Japan where there are significant numbers of slopes susceptible to failure. To understand the mechanisms and conditions leading to such failures, constant shear stress tests that mimic the field stress path were conducted on a sandy soil taken from a natural sliding slope whose surface soils were moving. Water was infiltrated from the bottom and top of an initially unsaturated cuboid soil specimen at constant shear stress until failure. The effects of cyclic wetting and drying on the deformation characteristics and four parameters reflecting the initial conditions, i.e., the dry density, overburden pressure, rainfall intensity, and slope angle, as well as various parameter combinations, on the time and moisture content allowing for failure initiation were investigated. The experimental results exhibited a unique relationship between the deformation and moisture content and suggested a relationship for predicting the time and moisture content of onsets of landslides based on the four parameters. The results obtained can serve as guidelines for the design of landslide hazard detection systems and mitigation measures against rainfall.