Evaluation Of The Risk Of Water Breakout From The Roof Of A Tectonically Complex Mine

The Jining No.3 coal mine is located in the southern part of the Jining coalfield,and the coal-bearing strata are the Taiyuan and Shanxi formations of the Carboniferous～Permian system,the main recoverable coal seam is the Lower 3 coal,and the main water-filled aquifers are the sandstone aquifers at the top of the coal seam and the Jurassic sandstone fissure aquifers.The field is strongly tectonically developed,especially the faults are distributed throughout the field and are intricate and complex,cutting the coal seams and having a large impact on coal mining.And according to the mine’s past production data,underground mining has repeatedly occurred in the roof burst water,mine surge（burst）water volume by the high degree of tectonic influence.Therefore,this paper takes the Jining No.3 field as the research object,evaluates the degree of structural complexity of the mine on the basis of systematic analysis of the geological and hydrogeological conditions of the study area,analyses the movement and deformation pattern of the coal mining overburden at the fault,makes an evaluation of the water-richness of the aquifer within the development of the water-conducting fracture zone of the roof,and predicts the zoning of the water hazard of the coal roof.Firstly,the fracture tectonic fractional dimension value,fault frequency density,fault scale index and fold plane deformation coefficient were selected as indicators for the quantitative evaluation of mine tectonics,and the grey fuzzy comprehensive evaluation method was used to quantitatively predict and evaluate the geological tectonic complexity of the study area,which was classified as tectonically simple,moderate,complex and extremely complex based on the calculation results,with the tectonically moderate and tectonically complex areas being the main ones in the study area.After that,FLAC^3D numerical simulation software was used to study the deformation of coal mining overburden and the development of fissures under the influence of strike faults and trend faults at the working face.The water-richness of the aquifer within the height range of the hydraulic conductivity fracture zone was evaluated according to the fracture development of the roof slab.Five factors affecting the water-richness of the aquifer were selected:the thickness of the aquifer,the thickness ratio of the brittle plastic rock,the number of sand mudstone interlayer,the core taking rate and the depth of the aquifer,and an evaluation model based on the independence weight coefficient was constructed to evaluate the water-richness of the coal roof aquifer under the study area 3,which can be divided into weakly water-rich,moderately water-rich and strongly water-rich zones.Finally,considering the complexity of the geological structure and the influence of the water-richness of the aquifer on the water hazard of the mine roof,the two are superimposed to obtain the predicted zoning of the water hazard of the roof of the coal mining under the study area3:safer zone,more dangerous zone,dangerous zone and extremely dangerous zone.The research results of the thesis have certain theoretical research value and practical guidance significance for the prevention and control of water hazards in the mine.