| Yangdong mine is located in the east of Fengfeng mining area.In recent years,Fengfeng mining area extends to deep coal seam.The mining area and mining depth of the coal mine are increasing,which makes the complex geological and hydrogeological conditions more complex,and there are unknowns and uncertainties.The Ordovician limestone aquifer has developed karst fissures,strong water yield and large water pressure.As a result,the Ordovician limestone aquifer is more and more threatening to the safety production of deep coal seam,and the risk of water inrush and the difficulty of water control in coal mine are increasing.The risk assessment of Ordovician limestone water inrush in coal seam floor can analyze the situation of water inrush and provide guarantee for water prevention.The numerical model of groundwater flow in Yangdong coal mine is established to study the change of permeability coefficient before and after grouting,and to scientifically predict the dynamic change of Ordovician limestone water level and flow field under the condition of coal mining,so as to provide strong guarantee for the safe mining of deep coal seam.Based on the data of Geology and hydrogeology of Yangdong mine,the characteristics of groundwater recharge,discharge and runoff are analyzed.The water inrush risk of 9 coal seam floor in Yangdong mine in Fengfeng mining area was evaluated by using the method of five graphs and double coefficient.In addition,the change of permeability coefficient before and after grouting is simulated by Visual MODFLOW software,and the dynamic changes of water level and flow field of ash water before and after grouting are predicted under the condition of coal seam mining.The following research results have been achieved:(1)The coefficient of pressure is less than 0 MPa and the coefficient of water inrush is more than 0.1 MPa/m.In the evaluation,the importance of effective protective thickness of floor aquiclude is considered.The three evaluation indexes adopted in this study are effective aquiclude thickness,pressure coefficient and water inrush coefficient;The effective aquifuge thickness of some areas is 0 m,which belongs to the straight through water inrush risk area,and the possibility of water inrush in this area is great.(2)The change of permeability coefficient of grouting is simulated by Visual MODFLOW software.The hydrogeological parameters are obtained by constant parameter adjustment.The hydrogeological parameters of aquifer before and after grouting are not changed much,and the influence of grouting on the aquifers of daqinglimestone is almost no,and has a certain influence on the aquifers in karst fissure of Ordovician limestone,but it has little influence;The relative aquifers have changed greatly.After grouting,the thickness and strength of the relative aquifers become larger,and the permeability becomes smaller,and the permeability coefficient is 2.8×10-5 m/d becomes 1×10-7 m/d.(3)Visual MODFLOW software is used to simulate the dynamic changes of Ordovician limestone water level and flow field before and after grouting under the condition of coal seam mining.The 10-year simulation shows that a funnel centered on Yangdong mine is formed;The water level drop of Ordovician limestone water is 15-20 m before grouting and 2-3 m after grouting.The water level drop of Ordovician limestone water after grouting is about 15 m smaller than that before grouting;Coal seam floor grouting can protect 4.95×107 m3 Ordovician limestone water resources,and coal seam floor grouting can effectively reduce the risk of water inrush,so as to improve the safety of coal mine production. |
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