| High-effect is the directions of the coal industry development in China, and is also a mark of advanced coal level of all developed countries in the world. In recent years, excavation of shallow coal seams in many mines is finished, and the excavation is gradually started into the deep part coal seams. The comprehensive conditions of mining become extremely complex, such as limestone karst water affected dozens of mining area in the North China type coal field, water inrush is occurred frequently in coal karst aquifer. Grouting reconstruction of coal seam confined aquifer is undoubtedly a best way to solve the water inrush accident. Grouting can eliminate or reduce the karst water bursting by make the high aquifer into weak aquifer or water-resisting layer.Coal karst grouting is a complicated hidden engineering. Its flow processes and grouting are common affected by structure of rock mass, features of karst confined water, magma character and grouting technology. This paper studied the following aspects based on the analyses of present grouting theory, material and methods.Using the trend surface analysis method, the water-resisting layer’s law of No.6 (10) coal floor is determined by studying the lithology of coal floor and reveal information of mine. And the structure of rock mass is divided into four types:the complete structure, the block crack structure, the cataclastic structure and loose structure based on the quantitative evaluation of the rock mass fracture developing degree by using the fractal theory and the fracture fractal dimension value.The orthogonal test of slurry mixture ratio shows that the slurry of expansive soil-cement has a higher stone rate and a better water plugging effect than the slurry of clay-cement during the grouting with the same grout proportion of and floor conditions, and the project of the lower cement ratio enjoy a cost advantage. Meanwhile the cement content has a significant effect on reinforcement impact of floor, but the clay content has a effect on water plugging effect impact.A test device called as multi-functional geological engineering model test system is developed to simulate the grouting at situ fractured rock. The simulation by using the system indicates that the impact of dynamic water pressure of groundwater on the fractured rock mass grouting is larger than the impact of confining pressure under the condition of single factor. Use the system the grouting test which under the condition of Groundwater hydrodynamic pressure and confining pressure shows that the dynamic water pressure increases 31 percent caused by coupling of confined aquifers and grouting, and the grouting pressure should be greater than the sum of dynamic pressure and initial target pressure.Based on the developing degree of limestone karst-cranny and rock mass characteristics, a geological model of spatial structure for four kinds of limestone karst aquifer is established. Some numerical simulations are carried out by using COMSOL Multiphysics, and the diffusion distances of four kinds of grouting with groundwater pressure are achieved.The accuracy of the optimized grouting parameters is proved in a field test by analyzing the water yield and slurry diffusion radius. The best method for effect assessment of coal floor karst grouting named as misering-geophysical prospecting integrated method is proposed, and it have been validated on the grouting effectiveness evaluation in No.633 coal face of Liuqiao mine. |
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