Research on response characteristics of loess slope and disaster mechanism caused by structural plane extension under excavation

Geological disasters occur frequently in the Loess Plateau due to the joint fissures in the strata and human engineering activities. Against this background, the deformation and failure mode of the loess slope with the structural plane under excavation and the extension mechanism of the structural plane are analyzed and summarized. The results showed that: (1) Through the physical model test, the deformation failure mode of the slope is summarized as the tension-splitting, pressure-sliding shallow failure. The collapse failure process is defined as four stages: Compression deformation, creep deformation, slip deformation and slip failure. (2) Slope displacement is concentrated beneath the pressure plate, increasing linearly under load conditions but becoming nonlinear after excavation conditions. As the excavation angle rises, the displacement range along the structural plane gradually extends toward the slope toe. The displacement time-history curve shows three stages: The lifting load stage, the cumulating deformation stage, and the sliding failure stage. (3) The stress redistribution caused by excavation, prompting deformation and potential failure. As internal stress nears the soil strength limit, human-induced disturbances exacerbate stress redistribution, leading to accumulated stress. Finally released through deformation and cracking. Each excavation condition modifies the original loading transfer path, driving stress redistribution at the slope surface and at the structural plane's tip. (4) The sudden drop in stress level and sudden rise of accumulated settlement are the characteristics of slope sliding failure. The position of the structural plane determines the position of the slope sliding surface. (5) According to the external characterization of the structural plane, the extension process of the structural plane can be defined as four stages: Initiation of crack extension, classification deformation, subsection extension and compression sealing. According to the extension of the structural plane, the spreading cracks of the slope's internal structural plane are defined as two types: Fractured cracks and shear cracks.