Study on mechanics mechanism and geological evolution model of large landslide in mining area

Many coal mines are located in the mountainous area，landslide disasters often occur，which seriously affects the normal production and life of the residents in the mining areas.Therefore，the study on the causes of landslide disaster is of great significance for the prevention and mitigation of geological disasters.The Junhong Road landslide in Fangshan District of Beijing was taken as an example in this paper.The microstructure and composition of the rocks that make up the landslide were analyzed by using micro-electron microscopy(SEM) and TTR Ⅲmulti-function X-ray diffractometer.The 2 000 kN rock single triaxial test system was used to analyze the landslide rocks.The mechanical properties were tested.The results show that the landslide body is mainly composed of metamorphic basalt from the Jurassic Nandaling Formation and gray-white gravel quartz sandstone from the Permian Shihezi Formation.Among these types of rocks，the clay mineral content is relatively high，with basalt of 36.1%，sandstone of 40.6% and conglomerate of 18.5%.Junhong Road landslide is a typical rainfall-induced landslide，which has experienced four stages： unloading tension crack，time-dependent deformation，local buckling and overall high-speed landslide.The content of clay minerals in the mineral components of several rocks that constitute the Junhong Road landslide is relatively high，and water has a significant effect on the mechanical properties of the rock.The uniaxial strength weakening of saturated water is 54.2% for basalt，40.0% for sandstone and 35.2% for conglomerate respectively，which play important roles in the occurrence and rapid start-up of the landslide under the action of rainfall.The structural surface plane is an important factor affecting the mechanical properties of rock.During the deformation process，the rock along the weak structural plane first breaks，and the rainfall further accelerates the failure of the structural plane，which is another reason for the occurrence of the Junhong Road landslide.