The mechanism of bending-toppling loess collapse caused by headward erosion

Abstract

Tracing erosion is the strongest dynamic geological action in loess hilly areas. It often causes the head of the ditch to retreat and the toe of the slope to be eroded, which in turn leads to collapse. Based on the statistical analysis of collapse disasters in the study area, this paper determines that the typical type of collapse caused by the traceable erosion effect is tension-toppling type. This type of collapse is characterized by steep back wall, rough wall, large scale, widespread, wide damaging range, and high potential risk. The formation of this type of collapse is mainly due to the transformation of the three areas in horizontal direction such as the tensile stress distribution area, the shear stress distribution area and the strong hydraulic erosion area under the action of surface water erosion and gravity. the collapse of slope undergone three stages: the increase and scope expansion of the tensile stress, the change of the shear stress state and the concentration of the scope, and the collapse of the collapsed body under the coupling action of the slope top tension and pore water pressure. The stability analysis can be carried out by the moment balance method. The three factors that affect the stability of the tension-toppling loess collapse include: slope geometric characteristics, soil physical and mechanical parameters and water pressure in the cracks. Theoretical analysis illustrates that with the increase of soil moisture content, the depth of tensile cracks on the top of the slope deepens, the depth of erosion grooves deepens, and the collapse stability coefficient gradually decreases.

Keywords

• headward erosion
• loess fall
• fracturing-topping type
• formation mechanism
• three zones and three stage