Risk Assessment Of Water Gushing (Burst) From Coal Roof Under The Influence Of Surface Gas Drainage Well

The implementation of ground gas drainage can not only solve the production hazard caused by high gas,but also realize the efficient use of energy.However,due to this effect,the extraction well is prone to deformation and failure in the process of stoping,and the overlying aquifer is communicated with to induce gushing(burst)water accident.In order to evaluate its effect on coal seam roof gushing(burst)water,the + 480 level in the west expansion area of zhangcun coal mine was taken as the research object,and the deformation and failure characteristics,modes,influence scope and degree of surface gas extraction drilling in the mining process were simulated with FLAC3 D software.On this basis,the risk of roof cracking is evaluated in combination with factors such as structure,and the water richness of the roof aquifer based on the optimal consistency matrix AHP method is evaluated for the risk of roof water inrush(burst).The conclusion is as follows:(1)By means of FLAC3 D and gas extraction in the process of mining ground deformation and failure characteristics of drilling simulation studies,mode and influencing scope and extent,the results showed that the existence of the gas extraction well increased the development of conductivity fracture zone height,without drilling water fractured zone maximum height of 119.94 m,there is gas extraction from the well water fractured zone maximum height of 138.94 m,drilling internal fracture conductivity with maximum altitude 151 m,and gas extraction Wells in the ground around the formation of the conical plastic zone radius of 15.86 m,the largest maximum height of24.02 m.The failure of gas extraction Wells located on both sides of the working face is mainly caused by axial tension and pressure,while the failure in the middle part is mainly caused by horizontal shear.(2)Based on the analysis of hydrologic and geological data,it is concluded that the main controlling factors of water-rich roof sandstone fractured aquifer are unit water inflow,aquifer thickness,permeability coefficient,fault size index,flushing fluid consumption,core taking rate,brittle plastic thickness ratio and fault density.According to the AHP method based on the optimal consistency matrix,the weights of the main control factors are 22.05%,21.11%,13.37%,10.87%,10.42%,10.41%,7.77% and 4.00%,respectively.Under the control of various control factors,water-rich regions of flaky regions appeared in the north-central,north-western,south-central and east-central regions of the study area.The overall water-rich regions in the central region were moderately water-rich,while the water-rich regions in the western and north-eastern regions were relatively weak(3)Using ArcGIS as well as the geographic information system database for multiple information fusion analysis,it is concluded that: gas drilling by the ground deformation and failure characteristics,scope of lead water fracture zones and structural factors,the study area water inrush risk areas are mainly concentrated in the north,northwest and east,and south and south-west danger zone is less,its risk mainly controlled by the ground gas extraction from drilling.