Effect of Rainfall Intensity on Landslide Initiation: Flume Tests and Numerical Analysis

This paper seeks to investigate the effect of rainfall intensity on the occurrence of shallow landslides by means of a series of flume tests. Coarse-grained material was used to build a slope, and several rainfall events with an intensity of either 40 mm/h, 70 mm/h, or 100 mm/h were simulated to initiate slope failure. A set of pore water pressure and moisture content sensors was installed in the slope to monitor changes in the water conditions during each test. Different initial moisture contents of 5% and 10% of the soil mass were used to better understand the effect of moisture on slope stability during rainfall. It was found that the slope failed when intensities of 70 mm/h and 100 mm/h were used; however, no failure was observed with a rainfall intensity of 40 mm/h. The failure patterns were found to be similar, with progressive slides occurring as more water infiltrated the slope. A numerical procedure to estimate the factor of safety over the period of the rainfall event was proposed and validated against the laboratory data. The results of the numerical analysis yielded the failure time, which was close to the time observed in the flume tests.