Instrumented model slopes to investigate the effects of slope inclination on rainfall-induced landslides

Rainfall infiltration is considered as one of the most significant factors triggering slope instability as a number of slope failure occurrences have been documented during or immediately after a rainfall. The rainfall-induced slope instability is governed by a complex interaction of topographical, hydrological and geological conditions of the slopes. Hence slope inclination is vital in determining slope stability under rainfall. Although studies have been carried out to investigate the mechanism of rainfall-induced slope failure, limited compelling experimental studies have been conducted on the factors influencing the initiation of slope failure. In this study, instrumented model slopes were subjected to artificial rainfalls to investigate the effects of the slope inclination on slope stability, and a validated numerical model was developed using the test results from the instrumented model slopes. The outcomes of the study prove that the slopes become more susceptible to sudden collapse during rainfall as the slope angle increases. Further, the results highlight that when the slope inclination is 1.2 times greater than the friction angle of the soil, the failure is initiated by the loss of soil suction, and when it is smaller than or equal to 1.2 times the friction angle of the soil, the failure is initiated by the positive pore water pressure developed at the toe of the slope.