| The water injection in coal seam to prevent rockburst has lower costing, simper operation and better availability, which is always the first selected measure. However, there is not a relative research result and it stops at test level. So, considering the rockburst prevention of greater gas content and higher porous pressure as background, the water injection in coal seam to prevent rockburst is researched. The main contents are as follows:1. The relation between the time of water immersing and water containing rate and the influence of destruction property of coal mechanical character are researched by test. The critical water containing rate of coal seam stability is determined. The water immersing time of full directed district is required. According to physic-chemical theory, the mechanism is illustrated that, by surface action of coal and water, water molecule enters in coal molecule, the distance between coal molecules becomes long and Van der Waals force decreases. Finally coal mechanical and destruction property is changed.2. The water injection in coal seam is practically a process that water enters coal seam by drilling holes and filters around holes to drive gas and occupies gas position. After the research on water driving gas, the mathematical model is set up. The previous process of water flow in coal seam as the analysis on seepage field of inhere water flow is changed.3. Regarding water and gas as incompressible fluid, the piston type water-drive-gas problems (which are appropriate for parallel radial flow among thick coal and planar flow among thin coal respectively) are solved. Regarding gas as compressible fluid and water still as incompressible one, the water-drive-gas problem appropriate for parallel radial flow is solved, so the relational expression about the water-gas interface changing with time is obtained, which may determine the needed time that the water costs to flow to designated site, that is, the time when the wetted area is filled with water, or the scope which can be full of water in designated time, so as to determine the advance water injection time and the layout scheme of drilling hole.4. Coal is typical double porous medium, not pure porous medium. To study thefluid flow among coal in the course of water-drive-gas water injection in theory, when water injection is carried out, according to the fact that coal is double porous medium, the differential equations set of water plane radical flow are discussed according to two kinds of condition. One condition is that assuming that the effect of adsorption and seepage is neglected, which is plane radical flow among double porous medium. In this case, the water molecule group can't enter the pore. Because the very narrow passage of pore, there is no fluid's flowing among the pores, and the flow is still single seepage among the cracks, which is similar to the previous condition mentioned in Chapter 5.The other condition assumes that the effect of adsorption and seepage is existing, in this case, the water enters the cracks driving the gas among them firstly and encloses the pores space of then expends the gas among pores into cracks, so after the water-drive-gas course, the region is divided into parts with different saturation degree, in which the flow is water-gas-two-phase flow, When the equation of adsorption and seepage is supplemented, the mathematical model of water and gas displacement is established ,which is plane radical flow taking the effect of adsorption and seepage .The location where it is the front may be got by the means of typical line, because the method is used to solve the relation between the location where the saturation degree is zero and time.5. The present and popular theory on how rockburst takes place is discussed. Because it is based on the instability theory about the mechanism of coal and rock failure, so it is suitable to the practice. To begin with this theory, the mechanism of water injection into coal seam to prevent rockburst from happening is discussed, and some examples at Wulong C...
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