Many slope stability studies have indicated that the infiltration of rainfall into a slope decreases its stability. And some of its mechanism has becoming understood. However

it remains an unresolved problem how to quantify the percentage of the rainfall infiltrating into a slope during a rainstorm. The model proposed by Holten on how to calculate the rainfall infiltration into a slope does not meet the precision requirements in practice. And most numerical models cannot simulate the true infiltration progress. Based on self-designed soil column tests

the process of rainfall infiltration has been studied. The results elucidate the mechanism of rainfall infiltration. An improved method for calculating the percent rainfall infiltration is proposed. A numerical model is used to shed further light on the rainfall infiltration mechanism not obtainable from the indoor laboratory experiments.