Hydrodynamic characteristics and failure mechanism of karst conduct flow on landslide under heavy rainfall

The geological environment of the karst mountain area is fragile. After heavy rainfall, the internal hydrodynamic conditions of the karst mountain change significantly, threatening the stability of the karst landslide. This study take Guanling landslide as a case study to clarify the influence of rapid karst conduit flow formed by heavy rainfall on karst landslide. Combined with field investigation and analysis of hydrogeological conditions, the seepage influence mode of karst conduit flow was obtained: (1) In the dry season, karst conduit flow seizes the bedrock debris flow head on both sides, erodes it downward, and expands the depth of the karst conduit system; (2) When heavy rainfall occurs, karst pipes flow to both sides and recharge, forming a watershed. The fluid-structure coupling numerical simulation experiment was carried out using two-dimensional discrete element coding UDEC software. The results showed that the transmission of high-pressure water head from the top recharge area to the foot of the slope had lagged for one hour. The drainage capacity of the clastic rock area at the foot of the slope was limited, which made the high-pressure water head conducted by the overlying karst conduit flow unable to be discharged in time. The retained high-pressure water head caused shear failure at the foot of the slope. It caused the overlying height difference of nearly 200 m sliding body and the landslide disaster. The instability mechanism proposed in this paper can provide a reference for other landslides induced by karst conduit flow and provide theoretical support for predicting and preventing such landslides.