Abstract: Typhoon rainstorms occur frequently in the southeastern coastal areas of China. The infiltration of rainwater under typhoon rainstorm conditions is an important cause of landslides in hilly mountains. Therefore, it is of great significance to study the migration law of rainwater infiltration wetting front under different geological environmental conditions. The temporal and spatial changes of rainfall infiltration were analyzed based on the monitoring data collected by the in-situ test of a landslide. A comprehensive rainfall infiltration model was established, which takes into account the nonuniform distribution of the initial water content of the soil and the slope environment. Then this model was verified by comparing to field test results and the predictions from existing classic models. The results demonstrate that: 1) At the initial stage of rainfall infiltration, the increasing slope of water content at different depths was steep. With the increase of time, the slope gradually slowed down. When the accumulated amount of rainfall reached 44.4 mm or more, the shape of the water profile changed from "Z" to reverse "S". As the rainfall intensity decreased, the type of rainwater infiltration process changed from water infiltration to non-water infiltration. At the later stage of infiltration, the growth rate of water content at different depths tended to be constant, and a stable infiltration stage was reached. 2) The migration speed of the wetting front increased with increasing rainfall. At the beginning of the rainfall, the rainwater infiltration rate was large. The migration speed of the wetting front was fast, and it decreased with the increase of soil depth. 3) The results of wetting front depth change over time calculated based on the improved rainfall infiltration model are consistent with the field monitoring test results, indicating that taking into account the slope angle and the inhomogeneity of the initial water content distribution can improve the accuracy of the predictions of the Green-Ampt model. The research results can have a certain significance for establishing an effective early warning model for landslides induced by the typhoon rainstorm.

Key words: in-situ monitoring, volumetric water content, wetting front, Green-Ampt model