| With the exploitation and utilization of coal resources in China, shallow coal resources almost depleted, coal mining has entered a period of deep mining, the mining environment is getting more and more complicated, hard roof control is an important aspect. The survey showed that nearly40%of the fully mechanized coal face belongs to pressure the strong hard roof. Therefore, to study and master the hard roof control theory and technology, has important practical significance.Hard overhead caving-blasting and high pressure water is commonly used in fracturing method. Blasting weakening law fracturing range, high efficiency, fracturing effect, but extensive use of explosives will pollute the underground environment, dangerous jobs in the gas-rich region, the little careless may cause a gas explosion, collapse seam. issues; safety of high-pressure water fracturing method does not affect the face excavation work, do not pollute the underground environment, but by the joints of roof rock, mineral composition, cementation of factors. Based on the above analysis, this paper presents the sleeve fracturing method applied to the roof fracturing and analyze the fracturing mechanism, the main results are as follows:(1) A brief introduction to the basic nature of the rock, focusing on analysis of high-pressure water fracturing mechanism and sleeve fracturing mechanism. Analysis of high-pressure water fracturing divided into two aspects of the sleeve fracturing mechanism is equivalent to a high-pressure water fracturing of the fracturing and weakening role. The sleeve fracturing single hole fracturing and porous control fracturing found by analyzing the porous sleeve control fracturing based on the need to control the direction of crack propagation, but the propagation direction of the maximum principal stress and the hole spacing.(2). As the background of xieqiao coal mine13216working face, on the basis of previous analysis of the stope mining pressure and behavior law, the caving roof initial and periodic step formula13216Face theory the Xieqiao mine collapse step down distance. The numerical simulation model, step away from the roof initial and periodic collapse, through simulation, through the establishment of appropriate caving criterion derived from breaking down at first step consistent cycle caving step distance slightly less than the calculated value. Through theoretical analysis and numerical simulation to determine the roof mechanical model more reasonable with Yanban calculated.(3) Establish an experimental model, to study the mechanism of sleeve crack and analysis the influence factors of Sleeve fracturing roof.. It was found that the sleeve fracturing effect by the pore size, pore spacing and sleeve pressure factors. When the hole spacing for the fixed value, as the hole spacing increases, the fracturing pressure increases, the maximum principal stress control reaches a certain level, the crack propagation; when the radius of influence is a fixed value, with the radius increases, the fracturing pressure decreases, in other words, when the fracturing pressure for the fixed value with increasing radius, fracturing range with the increase. Taking all these factors, the use of large-diameter is better.(4) Based on model experiments, to establish numerical model, the and numerical simulation analysis. Through simulation, we found that in the case of gradually increasing pressure, through X, Y-direction stress cloud, hole rapid redistribution of stress in around. When the pressure reaches the breaking pressure, along the direction of the arrangement hole, the Y-direction tensile stress exceeds the tensile strength of the rock, so rock fracture. By numerical simulation, adopt large diameter obtain the best effect, the simulation results the conclusion is consistent with the model experiment.Through theoretical analysis, model experiments and numerical simulation to analyze the sleeve fracturing method and the feasibility of its application, provide some reference significance for hard roof caving... |
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