| Coal resources in western China have the characteristics of thin bedrock,large res erves,excellent coal quality,shallow buried depth and simple geological conditions.C oal mining under thin bedrock is easy to lead to water inrush and sand inrush accide nts.Due to the thin bedrock above the coal seam,the development of mining fracture s to the aquifer will cause water inrush and even sand inrush,which will bring great hidden dangers to the safety of mine production and workers.Therefore,it is of greatsignificance to study coal mining under thin bedrock to ensure mine production.In this paper,taking the first mining area of Zhuanlongwan Coal Mine as the res earch object,the existing survey data of the mine are analyzed,and the engineering g eological conditions and hydrogeological conditions of the study area are summarized.According to the thin bedrock of Zhuanlongwan Coal Mine,the total stress-strain per meability test and acoustic emission test of different depths and lithology are carried o ut.The test results show that the total stress-strain permeability fracture of rock can b e divided into four stages : pore compaction density,elastic deformation,stable fractur e and strain softening.Through the change of ringing count and energy rate in differe nt stages of acoustic emission experiment,it is verified that the four stages of deform ation and failure in the process of total stress-strain permeability test can better reflectthe generation,expansion and penetration of cracks under mining conditions.Taking t he 231S06 working face in Zhuanlongwan as an example,based on the field measure ment,the height of fractured water-conducting zone is determined to be 92 m,and the calculation results of the empirical formula are 72.08 m and 75.52 m,respectively.Base d on the numerical simulation software,it is known that the working face advances 240 m,the height of fractured water-conducting zone has been developed to the Zhiluo group(46m),the working face ismined to 550 m,and the height of fractured water-co nducting zone is developed to the maximum value of 80.23 m.Finally,the average hei ght of fractured water-conducting zone is determined to be 80 m.Based on the above analysis,12 groups of orthogonal experiments were designed to study the influence of different mining factors on the height development under thin bedrock.The second-ord er response surface model equation of mining under thin bedrock was determined base d on the response surface method,and Analysis of the effect of the interaction of mi ning height,bedrock thickness,and quaternary thickness on the height of the hydraulicfracture zone.The Design Expert software was used to carry out the significance ana lysis of the second-order response surface model,analyze the deformation and failure characteristics of overburden rock,and optimize the mining parameters for 231S06 wo rking face.Fuzzy analytic hierarchy process and entropy weight method are used to s elect bedrock thickness,coal seam thickness,base-mining ratio,base-load ratio,water-r esisting layer thickness and hard rock ratio as the main control factors.Based on Arc GIS platform,FAHP-EM evaluation model is constructed to determine the final weight.The natural classification method is used to determine the interval threshold,and the risk zoning of water and sand inrush in Zhuanlongwan Coal Mine is carried out.The n,based on the catchment corridor method,the water inflow of Quaternary phreatic w ater and bedrock weathering zone in the working face were predicted,and preliminary suggestions for the design of water prevention and drainage system in the working fac e were put forward according to the actual situation. |
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