Research On Surrounding Rock Control Of Gob-side Entry Driving Of Fully Mechanized Top Coal Caving Mining Face With Large Mining Height

Tashan coal mine exploits extra-thick coal seam,with an average thickness of 15 m,and with an annual output of more than 10 million tons.Due to the large mining height and high-intensity mining,coal pillar width of working face has been left 38~45m,resulting in a loss of 1 million tons per kilometer of coal.In addition,the roadway is in the high stress area of the lateral support pressure,which leads to the occurrence of more serious impact rock pressure phenomenon,serious deformation of roadway,difficult to maintain and threatening the safe production.In order to solve the above problems using gob-side entry driving technology with 6m pillar,this paper is carried out by using field measurement,theoretical analysis and numerical simulation experiment.The main research results are as follows:(1)The activity range of the end face overburden rocks in the longwall top coal caving face with extra-thick coal seam and the laws of the overlying rocks fault were analyzed.The establishment of the end face structure mechanics model,triangle slip zone and its motion pattern were studied.The characteristics of the immediate roof and the basic roof were analyzed,and their definitions were given.The characteristics of the transitional structure of the front and rear part of the gob were analyzed,the stability of the end face structure and the effect of mining thickness on the end of the rock structure were studied.(2)This paper analyzed the time,space and intensity evolution laws of the lateral stress field and the end face roof structure of the longwall top coal caving with extra-thick coal seam,and studied the distribution rules of the lateral bearing pressure with the change of the structure of the mined-out area.The influence of the thickness of the coal seam on the end face structure and the lateral bearing pressure was studied,and the reasonable position and timing of the roadway driving along the road were determined.It was found that the decrease of the force acting on the coal pillar after the breaking of the triangular slip zone is the fundamental reason for the decrease of the lateral abutment pressure.(3)The deformation mechanism of the roadway along the gob driving was analyzed,and the deformation of the surrounding rocks of the roadway driving along the gob was revealed.The deformation of the surrounding rocks of the roadway driving along the gob was controlled by the rotation deformation of the upper rocks and the slip of the triangular slip zone.The distribution laws of internal strain energy density in coal pillars with different width of coal pillars was analyzed.The sudden release of internal strain energy in coal pillars was the root cause of impulse rock pressure.The additional stress field of anchor and anchor cable is obtained by numerical simulation.The characteristics of continuous bearing structure with different strength are formed in deep,middle and shallow parts of roadway surrounding rock,and the support scheme of roadway driving along gob is determined.(4)The relationship between the damage strain and the permeability coefficient of the coal pillar of the along gob side entry driving roadway was studied.The gas flow laws of the gob and the adjacent working face were analyzed.The “three-zone” distribution of the spontaneous combustion in the mined-out area was simulated,and the law of gas migration in the working face was also simulated.The integration of “injection-pumping” and the comprehensive safety and security measures during the mining period were put forward,which ensures the safe and efficient production in longwall top coal caving panel with gob side entry driving.