| Coal mines districted in Shanxi,Xinjiang,Shaanxi,Inner Mongolia,Ningxia,and Gansu account for 70% of China's annual average coal output,and the percent of extra-thick coal seam in these districts has reached 100%.The unclear mechanism of surrounding rock deformation characteristics of coal roadways under fully mechanized top caving and intensive mining within extra-thick coal seam has been a key problem affecting the safety production of each mine.In this paper,the Tashan coal mine was used as an engineering background,and comprehensive methods were adopted,including field observation,numerical simulation,similar simulation,mechanical calculation,and on-site monitoring.The main research contents were respectively the failure mechanism of surrounding rock-support structure in mining roadway with fully-mechanized top-coal caving face,the distribution characteristics and influencing factors of abutment stress in fully mechanized caving face of extra-thick coal seam,the stability-broken evolution characteristics of surrounding rock of mining roadway in fully-mechanized caving mining face,and comprehensive characteristics of surrounding rock of fully mechanized top-coal caving face in extremely thick seam.The main research results were as follows:(1)A large number of investigations and on-site monitoring were conducted around the deformation/destruction characteristics of the surrounding rock and support members in the mining roadway of a extremely thick coal seam in Tashan Coal Mine,revealing the overall deformation characteristics of the mining roadway with strong mining in a extremely thick coal seams,the main types of support structure damage,and the distribution status.(2)Established a mechanical calculation model for the fixed-supported beam combination of coal and rock layers in a extremely thick coal seam mining roadway,and the mechanical criteria for the shear breaking of the roof cable and the separation of the roof were deduced respectively.(3)The distribution characteristics of the plastic zone of the surrounding rock in the return airway under different width section coal pillar conditions during the mining of fully mechanized top-coal caving face are simulated and the relationship between the leading bearing stress,the advancing speed of the working face and factors of the coal caving method is explored.Monitoring results show that the overall distribution characteristics of the supporting stress in the fully mechanized caving face of extremely thick coal seam during mining process.(4)Through the pull-out strength test on different materials(such as iron wire,aluminum wire,fuses,etc.)and different diameter(0.8mm,2mm,1.5mm,etc.),the similar simulation material of bolts/cables in the typical mining roadway of extremely thick coal seam was optimized,and based on the similar material simulation method,the shape evolution,deformation and stress distribution characteristics of the surrounding rock of the extremely thick coal seam in different mining stress conditions were obtained.(5)Combining the production geological conditions of the 8110 working face in Tashan Coal Mine,a method for monitoring the deformation of the surrounding rock of roadways in extremely thick coal seams was proposed.The on-site monitoring obtained the mine pressure shows comprehensive characteristics of the evolution of the strata,the change of anchor/rope load,and the surrounding rock deformation in the 5110 return airway under the influence of two mining operations. |
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