A Study On Reasonable Retention Of Coal And Rock Pillars In The Mining Of Top Coal By The Yangliu Fault In Wugou

The 81 mining area is the main mining area to be mined in Yuandian No.1 well coal mine.The main mining is 8 coal seam.The 815 working face is the first mining face of the81 mining area,which is located in the north wing of the Wugou-Yangliu fault.Due to the large drop of the Wugou-Yangliu fault,the original design adopts the layered mining to set up the fault waterproof coal pillar of 250m.Now it is ready to adopt the top coal caving mining technology with higher efficiency,and the 815 working face is located on the hanging wall of the Wugou-Yangliu fault.Therefore,it is very necessary to carry out the research on the reasonable setting of coal pillar in 81 mining area.On the basis of consulting the research results of fault water inrush mechanism and reasonable setting of fault coal and rock pillars at home and abroad,this paper collects the hydrogeological engineering conditions of 81 mining area,and systematically analyzes the distribution characteristics of each aquifer and the water filling factors of working face.Two surface faults and Ordovician limestone water-rich hydrological exploration boreholes were designed and constructed.The rock samples of the roof and floor of No.8 coal seam,the fault zone and its Ordovician limestone aquifer were taken.The microscopic particle composition analysis,rock mechanics parameter analysis test and water physical property test were carried out in the laboratory.The water-bearing（water-conducting）characteristics of the fault and the development of limestone karst fissures and water-rich characteristics of the Ordovician limestone layer on the opposite side were basically identified,and the barrier water characteristics of the fault zone were revealed.The engineering geological model was constructed,and the FLAC^3Dnumerical software was used to simulate the evolution law of stress,strain and plastic zone in the process of coal seam mining with different fault protection coal pillars.Based on the theoretical calculation formula of the width of fault waterproof coal pillar in the’Coal Mine Water Prevention and Control Rules’,combined with the conclusions of experiment and numerical simulation,the width of rock pillar in the first mining 815 working face of 81 mining area is determined.The completed work and the corresponding results are as follows:（1）Based on the data of fine 3D seismic,upper and lower drilling on both sides of the fault and the contour line of coal seam on the hanging wall and footwall of the fault,the systematic research and analysis are carried out.It is concluded that the Wugou-Yangliu fault in 81 mining area is a normal fault,with an inclination angle of about 50～75°and a drop of 140～420m.It has the characteristics of small shallow drop and large deep drop.The 81 mining area is located on the hanging wall of the fault,and the drop in the mining area of 815 working face is greater than 320m.The mining is mainly threatened by the Ordovician limestone water and fault water.The original design of coal seam waterproof coal pillar is 250m.（2）According to the hydrogeological conditions of 81 mining area,aiming at the Ordovician limestone aquifer in the 815 working face,in order to find out the water abundance of the Wugou-Yangliu fault and the Ordovician limestone aquifer in the opposite plate,two pre-mining hydrological exploration verification boreholes were designed and constructed.The pumping test was carried out on the fault zone and the Ordovician limestone aquifer in the opposite plate,and the hydrogeological parameters were obtained.The unit water inflow q=0.00049～0.000733L/s.m and the permeability coefficient k=0.0024～0.0026m/d were obtained,which indicated that the water abundance of the Wugou-Yangliu fault and the Ordovician limestone aquifer in the opposite plate was weak in the mining influence range of the 815 working face.It is a water-free fault.It provides a scientific basis for the rational setting of fault coal pillars.（3）During the construction of hydrological exploration verification hole,the rock samples of Ordovician limestone aquifer,fault zone and 8 coal roof and floor strata were tested,and the particle composition,mineral composition and chemical composition characteristics and physical and mechanical properties of coal roof and floor and fault mud were analyzed.Based on this,the hydrogeological,engineering geological properties and water conductivity analysis of Wugou-Yangliu fault zone were studied.（4）Based on the borehole columnar shape of pre-mining hydrology,the existing borehole data around the working face and the results of laboratory rock mechanics test,the engineering geological model is constructed,and the FLAC^3Dsoftware is used to simulate the dynamic change process of surrounding rock under the influence of excavation when different fault protection coal pillars are left.Through the study of the variation characteristics of stress,strain and plastic zone,it is found that the influence range of mining from coal pillar to fault is close to 100 m,and it is reasonable and feasible to set up coal pillar according to the theoretical settlement result of water-proof width of815 working face.（5）According to the different calculation formulas of fault waterproof coal pillar theory in’Coal Mine Water Prevention and Control Rules’,the reasonable width of fault waterproof coal pillar in Wugou-Yangliu coal seam of Yuandian No.1 Coal Mine is calculated theoretically.Through the theoretical calculation and analysis of fault waterproof coal pillar,combined with the analysis of numerical simulation software,the width of fault waterproof coal pillar is 120～135m.Figure[54]table[22]reference[96]...