Study On Deformation And Breakage Characters In Coal Seam Floor Of Coal Mining Above Confied Aquifer By Numerical Simulation And Engineering Application

Many coal mines in China suffer from the water in karstifred limestone aquifers.Water inrush is a serious disaster in coal mining. Therefore the study of the mining condion of rock layer's deformation and breakage characteristics is depth and perfect for water inrush mechanisms and controlling which has great theoretical and practical significance.Based on the study deeply about the FLAC^3D software of numerical simulation and the compute principle of solid and fluid, founding the three dimensional simulation calculating model of pressure confined water. With the method of numerical simulation, the paper analysis the distributing law of the stress, displacement and breakage fields of coal floor deeply, Using the method of orthogonal test to identify that the most significantly damaging factors were working face width. They are in turn confined water pressure,thickness of lining seam and mining depth. Afterward the paper analysises the first three factors including in deformation and damage of coal floor.Finally, the paper analysises the hydrogeological conditions and mining of suntuan coal mine's 1028 working face, founding the simulation calculating model to analysis the actual project.In addition,the application of fractal dimension into evaluating the Mechanical parameters of rock mass is discussed in this paper.Throughout the study,the main conclusions are made as follows:(1)The breakage depth of coal floor rocks is accelerating with the increasing of the working face width and the distanceof the working face.But this influence has its limiting ,when the scope of mining arriving the limiting ,the influence on macro from minging parameters on the working face to the breakage depth of coal floor begin to diminish ,even unrelate.(2)When the water power is low(such as 3MPa),the breakage depth and scope of coal floor don't have a remaked changing due to the changing of thickness of confining bed .At the time the thickness of confining bed is thin but the power is big,the rock mass under the confining bed will have a large scope of destruction in situ tension crack,in addition to the breakage of floor directly .The breakage depth and scope accelerat as soon as the increasing water power.with the thickness of confining bed increasing ,the directing breakage of depth and scope will decrease .At the same time ,the scope of destruction in situ tension crack under the confining bed is decreasing even disappearing.(3)The extent and scope of damage are all increasing gradually as the accelerating of water power on the condition of model of solid and fluid coupling .The rate of increasing is much biger than in the no-coupling condition.(4) Fractal Dimension(Dr)from theory and calculating is relating large to the RQD.Rock quality data(RQD)becomes low as soon as the Dr become large. The larger of Dr,the worse of rock quality .But when the RQD is likely the Dr of cores are not in the same.So to some extent, comparing to the RQD,The Dr can reflect the characterize of rock mass more suitable ,such as,uniformity integrity.(5) Based on the actual conditions of hydrogeological,engineering geology and mining,simulating the process of the 1028 working face.The result shows that the breakage depth is much lower to 52meters of the the thickness of confining bed during the process.So that there will be not an accident of water inrush.Some conclusions are made clear through the paper. Using the theory analysis and numerical simulation method can open out the stress fields,deformation and destroying characters, and destroying range and depth of rock mass in coal seam floor under the condition of mining, which is propitious to select and optimize design projects, reduce the testing time and economize the project outlays, and then improve the economy benefit and society benefit.