Erosion effect in the movement process of rapid loess landslide using an improved two-layer model

Erosion effect plays a significant role in the run-out process of a rapid loess landslide. This effect is manifested in bed entrainment and frontal plowing on terraced material during movement, leading to the volume amplification. Therefore, an improved two-layer model is proposed to describe the frontal plowing and bed entrainment in this paper. In addition, the bed entrainment rate is further calculated by introducing the bed entrainment physical model. The sliding mass and plowed material are assumed to be immiscible in this model, and the mechanical behaviour between the materials is simulated by considering the interaction force between the two layers. Furthermore, the governing equations are deduced from the mass and momentum conservation. It is then applied to analyze a typical rapid loess landslide, Dongfeng landslide. The results indicate that the bed entrainment and frontal plowing have a significant impact on the mobility of the landslide, which is mainly shown in the following two aspects: 1) the bed entrainment effect significantly increases the speed and volume of the landslide; 2) The frontal plowing effect will impede the motion of the frontal sliding mass, and there is a clear separation between the sliding mass and the plowed material, which is more consistent with the field observations. The improved two-layer model proposed in this paper can provide more reliable assessment to describe the rapid loess landslides with erosion.