Study On The Failure Characteristics And Water Inrush Mechanism Of Stope Floor In Weibei Ordovician Confined Water Mining Area

In recent years,with the continuous expansion of coal mining in the Chenghe mining area,the coal floor is increasingly threatened by the high pressure water of the underlying Ordovician limestone,and the frequency of floor water inrush in the coal mine has increased significantly,which has seriously affected the safety production of the coal mine..Carrying out analysis of the mechanism of water inrush from the stope floor in confined water mining areas,and effectively curbing the occurrence of water inrush accidents in mines,has always been a problem that the coal industry needs to solve urgently.Taking the 22507 working face of Dongjiahe coal mine in Chenghe mining area as the engineering background,this paper uses a combination of theoretical analysis,numerical simulation and on-site monitoring to conduct an in-depth study on the failure characteristics of the stope floor and the water inrush mechanism in the Weibei Ordovician confined water mining area.The research results provide a scientific reference and valuable experience for the mining of confined water working faces in mines in the future.The main research results of the thesis are as follows:(1)Through on-site field investigation,the basic situation of Dongjiahe coal mine in Chenghe mining area,the working face engineering overview and hydrogeological conditions are introduced in detail;the main influencing factors of water inrush from the floor during coal seam mining are analyzed in detail,from the floor aquifer,Floor water barrier,geological structure,engineering mining and other four aspects are discussed.Provide guidance for studying the water inrush mechanism of stope floor in Weibei Ordovician confined water mining area.(2)According to the theory of mine pressure and rock strata control,the mechanical calculation models of the stope floor along the working face dip and strike under periodic pressure are established respectively,and the stress distribution law and failure characteristics of the floor rock mass along the working face dip and strike are analyzed by elastic theory.According to the theory of plastic slip line,the maximum plastic failure depth of stope floor is analyzed,and the width of plastic zone at the edge of coal body is determined by fracture mechanics.(3)The FLAC3D numerical simulation software was used to numerically calculate and analyze the failure characteristics of stope floor in the process of working face mining,and discuss the failure characteristics of the stope floor on the confined water under the influence of the advancing distance of the working face and the inclined length of the working face.In addition,the sound wave detection technology is used to conduct on-site measurement and analysis of the damage depth of the working face floor to further verify the correctness of the theoretical analysis.(4)Establish the mechanical model diagram of the key layer of the stope floor on the confined water,regard the key layer of the water-resistant layer as a rectangular elastic thin plate with four sides fixed,and use the method of theoretical analysis to study the area and floor when the stope floor is pre-destructed The location where the risk of water inrush is the highest;and the relationship between the hydraulic inrush criterion for the failure of the key layer of water-resistant coal floor is analyzed,and the relationship between the maximum hydraulic pressure that the key layer of water-resistant coal floor can withstand and various influencing factors are discussed.(5)The technical measures for grouting reinforcement and reconstruction of the coal seam floor failure zone and K2 limestone aquifer are aimed at reducing the depth of mining failure of the stope floor,increasing the thickness and overall strength of the key water-resistant layer,and transforming the K2 limestone aquifer into Key water-resistant layers or weak aquifers;electrical geophysical methods are used to compare the effects before and after grouting in the grouting area of the working face,and to evaluate the water blocking effect of grouting reinforcement and transformation.