Abstract: Quaternary deposits are widely distributed throughout southwest China. To address the distribution pattern of crushed stone layers within these deposits, a rainfall physical model test was designed specifically for deposits containing crushed stone interlayer. The test aimed to investigate the migration behavior of water and air within the deposits under intermittent rainfall through finite element numerical simulation. The results indicate that pore air pressure acts as a hindrance to rainfall infiltration in slopes. During the initial rainfall, pore air pressure is at its lowest level, resulting in the fastest infiltration speed. Following each rainfall event, the soil undergoes saturation redistribution from the transient saturated zone to the unsaturated zone, leading to the lag of the advancement of the wetting front during subsequent rainfalls. Pore pressure does not dissipate immediately after each rainfall, but reaches its peak later than the rainfall process. Moreover, as rainfall frequency increases, the peak pore pressure is further delayed. Crushed stone interlayers serve as primary pathways for air discharge. In comparison to homogeneous deposits, pore gas pressure in deposits containing crushed stone interlayer dissipates earlier and more rapidly, which, consequently, promotes water infiltration.

Key words: deposits containing crushed stone interlayer, intermittent rainfall, water-air two-phase flow, rainfall infiltration, model test