Study On Damage And Deformation Of Slope Rock Mass Caused By Underground Goaf

China is an area with frequent geological disasters.Statistics show that the occurrence of geological disasters is largely related to human activities.As the main factor of geological disasters induced by human engineering activities,the geological disasters formed by mining have the characteristics of large destructive force,wide influence range and large economic loss,especially the landslide geological disasters induced by underground mining are the most serious,resulting in many catastrophic accidents.Therefore,it is of great theoretical value and engineering guiding significance to study the evolution law of slope rock mass damage and deformation failure caused by underground mining,so as to provide reliable basis for comprehensive evaluation of slope stability and efficient coal mining.In this paper,the strength characteristic deformation characteristics,macroscopic failure mode,microscopic displacement field and crack propagation process of fractured limestone in the study area were studied and analyzed by taking the deformation body of mazhong ridge in manling town,nayong county,guizhou province as an example,and the damage evolution law of brittle rock under complex stress path was studied.On this basis,the state as the platform,developed with vc + + language to state called dynamic link library files,based on damage evolution constitutive model of fractured rock mass slope Ma Zhongling simplified model,simulates the mining-induced fractured rock mass slope under the influence of the bursting of the scope of damage evolution process,analyzes the types of slope failure mode,this paper expounds the deformation damage evolution law of slope damage.The main research results are as follows:(1)Deformation and failure of the mazhongling mountains are affected by both geological and non-geological factors.The direct cause of geological disaster is non-geological factors in coal seam mining,and the deformation and collapse of goaf cause uneven deformation adjustment of slope,which makes the originally stable mazhongling produce deformation and failure on the basis of its own unfavorable internal factors.The failure form of the slope depends on the topography and landform in the geological factors.The combination of "upper hard and lower soft" makes the slope have certain self-stability ability,which leads to the lag of the failure of the slope relative to the mining of coal seam and the formation of large vertical fractures.The structural characteristics of the rock mass composed of three structural planes cut the rock mass into blocks,providing boundary conditions for the occurrence of landslide,collapse and fracture of the slope mass.(2)Three stress paths are adopted to simulate different mining methods.Conventional triaxial loading means that the rock strength in natural state is the highest,and path 3 means that the rock strength of surrounding rock of goaf roof is the lowest.The size of confining pressure is closely related to the mechanical properties and deformation characteristics of rock.The increase of confining pressure makes the surrounding rock gradually transition from brittle failure to ductile failure,and the critical confining pressure is 20 MPa.Unloading causes more serious and severe damage than loading,and unloading causes a large number of axial cracks on the rock surface.Therefore,unloading failure often results in composite tensile and compression failure of the rock,and the acoustic emission count of unloading failure is much higher than that of loading failure.(3)This paper proposes the fracture rock mass damage evolution constitutive model and Voronoi discrete block model.From the point of view of engineering application,this paper systematically analyzes and summarizes the rules and characteristics of the fracture evolution of the surrounding rock mass from the perspectives of displacement vector field,principal stress vector field,plastic yield area and fracture damage area distribution.(4)Bottom friction test(qualitative)and UDEC simulation(quantitative)are combined to reproduce the whole process from deformation to failure of the collapse body.The results show that the deformation and failure of zhongling slope are caused by coal mining and goaf collapse in the lower part of slope,and the failure mode is toppling collapse.Evolution process is as follows: 1)due to coal mining at the bottom of the slope,formed when the large mined-out area,the upper goaf roof deformation and roof in the central area of the first cracking of rock mass damage,even collapse,the upper slope under the action of gravity stress compression ballooning,coal pillar provides space for the upper slope deformation and destruction of slope area table started to pull crack,and over time and the development of the track under the steep dip structure for extensions,promoted the trailing edge crack expand to the deep slope.2)uneven deformation of the slope leads to deformation failure of the whole slope,and differential settlement will lead to staggered cracking and vertical fracture of the rocks along the steep structural plane.The development of fractures destroys the integrity of the upper rock,which is composed of hard limestone and mudstone.There are many fractures parallel to the open surface on the top of the mountain.3)with the intensification of collapse in the goaf,coupled with long-term weathering unloading and dissolution,the cracks continue to expand and deepen until they break through,separating the upper rock mass from the bedrock,and the separated columnar rock mass keeps toppling outwards to form dangerous rock mass,until the collapse disaster occurs.