Abstract: Slope stability under rainfall is closely related to fissure-induced infiltration. In an aim of investigating the effect of fissure development on rainfall infiltration in deposits, two models were designed for the fissures developed on the surface of a huge accumulation body along the Lancang River: a model of primary-secondary fissures, and a homogeneous model for reference. Only the shape characteristic of fractures in the actual deposit was considered for the sake of ideal model size. The changes in the moisture content, matric suction, moving speed and depth of wetting front of soil were obtained through laboratory physical model tests and numerical analysis. In the whole time period of one-hour rainfall and 23-hour observation, the migration trend of wetting front can be summarized as infiltration acceleration, peak value, infiltration deceleration, and tending to zero in sequence. Thanks to the favorable channels provided by fissures, rainwater could reach the deep of the soil and form a transient saturation zone which gradually dissipates as the rainfall ends. The infiltration of rainfall in fissured deposits can be divided into four stages: complete infiltration in the early stage, intense infiltration below the fissures, compensated accelerated infiltration, and horizontal infiltration.

Key words: rainfall infiltration, model test, numerical analysis, accumulation body, wetting front