A large number of loess-bedrock fill slopes were formed in the large-scale gully land consolidation projects on the Loess Plateau, and shallow landslides frequently occur induced by rainfall. There are limited studies on the loess-bedrock fill slopes induced by continuous heavy rainfall, and the influence of the interface between the fill slope and the original bedrock slope on the hydrological process and failure mechanism of the fill slope remains unclear. In this paper, we carried out a continuous rainfall model test on a loess-bedrock fill slope. The responses of volume water content, pore water pressure, micro deformation, and wetting front migration during the test were monitored, and the hydrological process and failure mechanism were analyzed. The results indicate that the soil-rock interface is a preferential infiltration surface inside the fill slope, the infiltration rate of rainfall along the interface is 1.24-2.80 times that along the fill slope, and the peak value of pore water pressure at the interface is greater than that in loess fill. The wetting front moves rapidly along the interface to the bottom of the slope, which weakens the connection between the bedrock and loess and has a negative impact on the slope's stability. The failure of loess-bedrock fill slope induced by continuous rainfall can be summarized into three stages: local failure→flow slide and crack penetration→multistage block retrogressive slides. The cracks generated at the slope shoulder are the controlling factors for the boundary and scale of shallow landslides. Finally, some engineering prevention measures suitable for the prevention of loess-bedrock fill slope failure and erosion are proposed. These results provide theoretical support for the prevention of similar slope risks in gully land consolidation projects.
 

Soil-rock interface,Loess fill slope,Interface hydrological process,failure mechanism injection