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The deep mining of coal mines leads to some significant changes in the physical properties of coal and rock, stress environment and gas occurrence law. The perturbed range of overlying rock and level of dynamic-static load have also increased significantly. In addition, the disaster effect caused by the linkage of mine groups and the control effect of large geological bodies appear in deep mining. The same disaster effect with the coexistence and conversion of rock burst and coal & gas outburst occurs. Therefore, above characteristics make the prevention and control of dynamic disaster in deep coal mines become a problem to be solved urgently. Considering the situation that the conditions of disaster breeding and mutual transformation mechanism are complex and still unclear, the quick detection method, prevention- control technology and equipment are still lacking, in this paper, the key scientific and technical problems of prevention- control for dynamic disaster in deep mining are condensed, the thought of prevention and control with different sources in multi-scales for coal and rock dynamic disasters in deep mining is proposed, the research direction of prevention and control technology for dynamic disaster in deep mining is determined, and the theory and technical framework of prevention and control with different sources in multi-scales for coal and rock dynamic disasters in deep mining are established. Based on the above achievements, the theory and technology system of prevention and control with different sources in multi-scales for coal and rock dynamic disasters in deep mining are formed successfully, which can provide a theoretical and technical support for the prevention and control of rock burst, the outburst of coal and gas or compound dynamic disaster in deep mining of coal mines in China. [ABSTRACT FROM AUTHOR]

In Western China, there are some mining areas with complex geological structure and significant hazards of gas, coal and gas outburst. The outburst hazard not only threatens safety of mine gravely, but also makes it difficult to explore coal resources in some regions. Aiming at the characteristics of the complex structure, poor coal seam permeability and multi-seam mining in the mining area, with the purpose of eliminating the danger of outburst and decreasing the gas content of coal seam, this paper made a systematic research on the mining of the lower distant protective layer, the technology of pressure-relieved gas drainage using surface boreholes and eliminating the potential dangers of coal and gas outburst. By constructed the model of similar materials experiments of stope and numerical simulation, the author studied the depressurization effect of protected coal seam under the mining condition of lower distant protective layer: (1) During extraction of the lower distant layer, the stress of protected layer could be reduced sufficiently, and gas permeability coefficient could be increased substantially, providing favorable condition for gas drainage; (2) As the double protective seam mining,40-50 m area of intake entry and return entry of mining face in protected coal seams is dilated area, which is the proper location of surface boreholes; (3) Repeat depressurization mode is found that the gob of the extracted seam below the gassy one provides a "Buffering Effect" for the overlying coal seam which makes the depressurization of the overlying seam weaken. The results from mechanical model for analysis of the stability of surface borehole are: (1) The greater the difference between the strength of adjacent strata is, the bigger the squeezing and shearing stress in the casing become; (2) Under the condition of leaving the space between the casing and borehole wall, the max shearing stress of casing decreased by 50.8% evenly, and the probability of failure of casing was reduced significantly; (3) The longer the production casing is, the bigger the deflection value is and the greater anti-bending ability the casing gets. Based on the above results, the author designed a structure of surface borehole against shearing and rupturing. There leaves the "buffer spacing" between the cementing casing or borehole wall and the production casing which is whole-tube and screen section was handled by "casing enhancement technology", effectively improving the stability of surface borehole. The law of pressure relief methane drainage using surface borehole is demonstrated: (1) Illustrated the distance from working face to borehole (showing the methane permeability coefficients of overlying coal seam and fractured zone), is the key influencing factor of gas production rate of borehole; (2) Revealed the changing mechanism of "fast increase-slowly decrease" of the gas production rate of borehole during the protective coal seam mining, and determined the best layout parameters of surface boreholes; (3) Built a mathematical model for determining the gas flow rate of overlying coal seam and gob, which can provide a basis of assessment for gas drainage of overlying coal seam; (4) Proposed the method of improving gas drainage form overlying pressure released seams with increasing the lower borehole resistance. The research results mentioned above were carried out in Wulan Coal Mine of Shenhua Group, which show that the effect of eliminating outburst by extracting pressure relieved gas with surface boreholes is remarkable. The pure gas drainage quantity of boreholes in the testing area has totally reached 1 512.96 x 104 m³. The max spacing of borehole near the intake entry and the return entry are 150 m and 169 m respectively. The remaining gas quantities of the protected coal seams are eliminated to 3.63 m³/t and 3.14 m³/t, and the gas drainage rates are 65.8% and 68.0%, respectively, completely eliminating the outburst danger of the coal. [ABSTRACT FROM AUTHOR]