Mechanism of geological hazards in the middle Permian collapse in the Wulingshan mountains of Guizhou Province

The objective of this work is to analyze the mechanism of geological hazards of middle Permian collapse in the Wulingshan mountains, Guizhou Province. Based on field investigation and available geological data, it is found that the middle Permian strata in this area is mainly distributed on both banks of Wujiang river and its tributaries. The typical river valley terrain essentially causes the collapse. According to the analysis, the unloading action leads to the formation of vertical fractures in rock mass. These unloading fractures expand steadily under the combination of gravity, water erosion and dissolution, and other external forces, forming the boundary of dangerous rock mass. In the meantime, the unloading fractures together with independent structural planes such as layers and joints cut rock mass into independent dangerous rock masses, which leads to collapse. Three main types of failure modes of the Permian collapse in the region are proposed, unloading-stretching-overturn, unloading-stretching-sliding, and unloading-stretching-falling, of which the first type dominates the collapse in the study area.