A two-layer numerical model for simulating the frontal plowing phenomenon of flow-like landslides

Many flow-like landslides entrain material from their paths during motion. At the flow front and along the lateral margins the sliding mass can plow into the path material pushing or entraining the existing soil. Although plowing can be a dominant mechanism for landslide mobility, little attention has been paid to this phenomenon in comparison with other entraining mechanism such as basal scouring. Therefore, establishing a suitable mathematical description is still a challenge. In this paper, a two-layer finite difference model is proposed to simulate frontal plowing. The frontal erodible mass and the sliding mass are simplified as two separate layers based on the assumption that they are immiscible in their propagation processes. The interaction (i.e., thrusting and shear) between the two layers is simulated by the normal force and shear force acting on the two-layer interface. The governing equations for the two-layer model are deduced from the mass and momentum conservations of a soil column and transformed into a finite difference form for numerical solving. Then the proposed model is tested in the back analysis of the Ximiaodian landslide which is a typical loess flow-like landslide located at the south bank of the Jing River, China. The modeling results show that frontal plowing has significant influence on the propagation of this landslide, especially on the final topography of the deposit. Without considering this effect, the thickness of the final deposit tends to be underestimated, while the propagation duration, area and distance are likely to be overestimated. The proposed model can provide more accurate and reliable simulations for rapid flow-like landslides with frontal plowing phenomenon.