Study On Deformation And Failure Characteristics Of High Steep Rock Slope Under Mining Action

Rock slopes are widely distributed in the southwest mountainous areas of China.Most of these slopes are located in the areas with strong karst development.There are many steep joint surfaces in the slope body,and underground mining activities often exist below.The slope terrain is dangerous,the slope surface is "steep on the top and gentle on the bottom",the slope lithology is "hard on the top and soft on the bottom".The upper hard rock is mostly carbonate rock,which forms a complex under the dissolution of water Miscellaneous karst pipeline.Under the joint action of unique geological environment and underground mining activities,the slope body damaged by karst water erosion and weathering is very easy to lose stability.Therefore,the analysis of the deformation characteristics of rock slope under the action of mining will contribute to the study of the mechanism of deformation and instability of karst slope induced by underground mining.Based on the "8.28" mountain collapse accident in Nayong County,Guizhou Province,this paper studies the deformation and failure characteristics and stress transfer law of the mined out area under the rock slope through field investigation,theoretical analysis,indoor model test and numerical simulation.The research in this paper has certain theoretical significance for the research of deformation and instability mechanism of rock slope under mining action.The main research contents and achievements are as follows:(1)Based on the field investigation of the "8.28" collapse accident in Nayong County,Guizhou Province,this paper analyzes the engineering geological environment,underground mining activities and the development characteristics of slope ground fissures.(2)Based on the key layer theory,elastic foundation beam theory and beam plate theory,combined with the slope shape and boundary constraints,a semi infinite rock beam model for the settlement calculation of slope under mining action is established,the differential equation of settlement curve is derived,and the analytical formula of settlement curve is obtained by using the software of Mathematica,and the ground fissures at the back edge of the mountain are verified theoretically.(3)Based on the indoor similar model test,the deformation of slope body,the change of interlaminar pressure stress and the development of ground fissures are studied when the mined out area is under the rock slope.The results show that the angle of roof fracture inside the mined out area is smaller than that outside;the increase of interlaminar pressure stress occurs in the local area near the inner side of the mined out area;the ground fracture is vertical to the bedding plane and appears above the area where the interlaminar compressive stress increases.(4)FLAC3D software has carried on the numerical simulation research to the rock slope under the action of mining,analyzed the influence of mining depth,slope gradient and slope bottom width on the slope plastic area,displacement field and stress field,and found that: the plastic area of the roof in the inner side of the goaf is larger than that in the outer side of the goaf;there are three areas with constant maximum principal stress on the same rock layer;the maximum subsidence position of roof is shifted to the inner side of goaf.