Study On Rock Burst Under The Condition Of Roof Drainage In Water-Rich Mine

As the depth of coal mining increases year by year,complex geological conditions(high temperature,high ground stress,high gas and high water pressure)cause complex and changeable factors for rock burst.Therefore,under different geological conditions and mining engineering,the research on the mechanism,monitoring and prevention of rock burst has become an important scientific issue to ensure the safe and efficient mining of deep mines.Therefore,this thesis takes as the engineering background that after the roof drainage rock burst in water-rich area boundary appears more serious in recent years in mines including Binchang mining area in Shanxi,Ordos mining area in Inner Mongolia,and Juye coal field in Shandong.The mechanism,monitoring and prevention of rock burst generation under the condition of roof drainage are investigated systematically in the way of field investigation,theoretical analysis,laboratory and field tests.Conduct relevant research on roof hydrophobic engineering first;secondly explore the rules of rock burst occurrence and main hydrophobicity influencing parameters under different roof drainage conditions;transform the research on the mechanism of rock burst generation under the non-mechanical and mechanical action of hydro-fluid;and then apply the charge induction technology carry out rock burst monitoring research;finally,through the overall prevention system,practical prevention measures and parameters for rock burst prevention research.The main research contents are as follows:(1)The distribution of major mines in China where roof water-rich and rock bursts coexist was investigated,and the aquifer occurrence characteristics,hydrogeological types,and burst tendency coal and rock layers in each mine were collected.The method of water drainage on mine roof,the structure of water drainage hole and the drainage process and technology were mastered.The variation law of water output of and water pressure of roof drainage hole and the influence range of the drainage hole on the roof were clarified.The influence mechanism of roof drainage on rock mechanical properties under the non-mechanical and mechanical action of water fluid was analyzed.(2)According to the microseismic distribution law and borehole stress change characteristics from the mining working face to the water-rich zone,the influence law of the roof drainage on the working face stress adjustment was obtained indirectly.Through the analysis of the occurrence time,location,site damage and surrounding water drainage of multiple rock bursts,the characteristics of rock bursts under different drainage conditions were obtained.It is determined that the initial water volume and water pressure of the drainage holes are the key water drainage parameters that affect the occurrence of rock bursts.(3)The mechanical properties of sandstone in water rich areas under different flow environment and water rock interaction time are carried out,and the variation rules of mechanical parameters of sandstone under different flow environment and the functional relationship with water rock interaction time are obtained.The sandstone deformation characteristics test under the condition of water pressure unloading was carried out,and the law of sandstone deformation after water pressure unloading under different water pressure conditions was obtained.(4)According to the non-mechanical and mechanical effects of water fluid on sandstone,a mechanical model of roof hydrophobic stress transfer is established,and an analytical solution of coal seam stress distribution related to sandstone damage variables and water pressure is obtained.Taking a working face as an example,the stress evolution law inside and outside the water rich area after roof drainage is explored,and the key prevention areas of rock burst caused by roof drainage are obtained.According to the theory of disturbance response instability,a critical stress index method is proposed to quantitatively evaluate the impact risk of the inside and outside the water-rich area before and after roof drainage.(5)A force-electric coupling model under uniaxial compression is established,and a nonlinear conversion relationship between the loading stress and the cumulative amount of coal deformation and fracture process is obtained.The induction technology is used to monitor the changes of coal seam stress during the roof drainage,and the charge parameters of each measuring point in the water-rich area before and after roof drainage are compared and analyzed,the stress transfer range under certain drainage conditions is preliminarily delineated,based on the change of peak charge volume at each measuring point,the stress transfer characteristics under different hydrophobic amounts are obtained,and the area for prevention and control of rock burst is preliminarily delineated.(6)According to the temporal and spatial differences between the roof drainage project and the mining face,the idea of "staged" rock burst is proposed.According to the theory of disturbance response instability,the countermeasures of "control inside and prevent outside" are given for different prevention and control stages.Against the internal and external impact risk of the water-rich area before and after the roof drainage,the prevention and control parameters for depressurizing large diameter borehole,strengthening support and controling mining speed are determined.Pressure-relief effect of large-diameter boreholes is tested by the law of charge change.