Experimental and numerical study of shallow loess slope failure induced by irrigation

Abstract

Irrigation-induced shallow loess landslides on south bank of the Jing River, Shaanxi Province, usually occur on slopes where loess flowslides had previously occurred. Two groups of irrigation-erosional experiments were conducted to study the hydrologic characteristics and failure processes of unsaturated loess slopes. In addition, SEEP/W and SLOPE/W in Geo-Studio were selected to quantify the effects of soil suction, slope gradients and soil properties on the stability of the unsaturated loess slope. Results indicated that smaller slope gradients are associated with higher average infiltration rates, greater sliding surface depths, and farther sliding distances. However, the smaller the gradients of the slope, the longer irrigation times and more water are required for slope failure. There are four stages in the evolution of the loess slope during artificial irrigation: the erosion of slope surface - the generation of tension cracks at the slope shoulder - partial failure occurrence and generation of potential sliding surface - retrogressive slope failure. The suction strength is a dominant component of shear strength in maintaining stable conditions in small-scale loess slopes. The irrigation caused dissipation of soil suction in the near-surface soil, thereby reducing shear resistance and triggering shallow loess slide. However, the finiteness of the suction strength determines that its attenuation will not determine the stability of large-scale landslide. Our results have implications for the understanding of surface erosion and shallow sliding of small-scale loess slopes at South Jingyang Plateau.