Extension mechanism and failure mode investigation on a fissured loess slope induced by loading

The loess structural planes of different formation, scales, origin, and types are widely developed in loess slopes, which can significantly control the structure, hydro-mechanical properties, damage regulations and deformation failure pattern of the slope. A series of major engineering projects have been implemented on the Loess Plateau of China. These projects have formed many loess slopes, which are prone to failure induced by loading. However, the failure mechanism of heap-loading loess slope, especially the influence of structural plane on slope failure, is not clear. Therefore, based on the investigation and analysis of the characteristics of loess structural planes, a large-scale model experiment was carried out, and the deformation process and failure mechanism of loess landslide induced by loading were systematically investigated. The soil pressure distribution, plastic state, and deformation characteristics of the slope were analyzed to reveal the influence of the structural plane on slope failure. The results show that the existence of the structural plane changed the stress field of the loess slope, forming a preferential yielding region around the structural plane, making the structural plane more likely to become a potential sliding surface. Different increases of earth pressure in the x- and z-direction is the main reason for the change in the extension angle of the structural plane. The propagation of the shear zone presents a typical “double slip surface” structure. The failure process of the loess slope induced by loading could be generalized into structural plane extension, shear band initiation, shear band penetration, and sliding failure stages.