Evolution Of Water Quantity And Pressure During Sudden Water Inrush At The Working Face Near The Fault

Fault surge water is one of the most common water hazards in coal mine production,and the related water pressure identification of the aquifer and the analysis of the signs of protrusion are important safety work in the construction and production of related mines.There is a risk of a sudden surge of water during the mining process on the 3301-mining-face of Yixiao Coal Mine in Wenshang County,Jining City,Shandong Province.Because it is located on the upper of the fault zone when the lower of the Ordovician system ash formation is affected by the uplift of the fault,which shortens the linear distance between the water body and the working face.According to the comprehensive investigation of lithology,structure and water-richness between working face and fault zone and hydrogeological risk identification,the fault zone is the key risk source of possible mining sudden water,reinforcing and protecting the fault waterproof coal pillar is the key way to create mining safety conditions,and conducting observation of mining water gushing and water level of australopithecine tuff is an important safety technical measure.At the same time of piezometric test inspection and slurry reinforcement to form a fault waterproof coal rock column,two hydrogeological observation holes of Ordovician tuff were arranged in the lower plate of the fault,so that once the water gush occurs at a certain location downhole,it is possible to make timely judgment through water pressure observation.If we can identify how much suddenly the surge of water can be mined on the near-fault zone working face,what shape the cone of depression is,what specific observation point the water pressure is and other evolutionary characteristics,there will be greatly significant for judging the risk of the sudden surge of water.This thesis takes Yiqiao Coal Mine as the background,on the basis of the analysis of engineering geological problems and hydrogeological conditions,,comprehensively using experimental research,numerical calculation,and other methods after geological model generalization → experimental(calculation)model generalization → model design,and other processes.Through the above efforts,this thesis tries to explore the evolution characteristics of water pressure during the sudden inrush of water in nearfault working faces,making the following main conclusions:(1)Based on the hierarchical analysis method(AHP),five factors influencing the water pressure and evolution characteristics when the sudden surge of water occurs can be summarized as follows(in descending order according to the degree of influence):fault zone containing water conductivity properties,hydraulic transfer path,fault zone dip,the initial head,fault zone width.(2)By the model test analysis,in the free water conditions,the head evolution curve is divided into: the initial head,the occurrence of sudden surge of water instantaneous pressure "diving",pressure back up,tends to stabilize,restore the head of water and so on five stages,flow-time curve presents: seepage stage,sudden surge stage,stable stage.In the fixed surge stage,surge water and sudden surge of water instant pressure " diving " water level,stable head there is a clear negative correlation.(3)When the sudden surge of water occurs instantly,there is a pressure "diving" and flow surge phenomenon,and with the increase in the width of the fault zone,the pressure "diving" amplitude is greater,sudden surge of water instantaneous surge flow rate also increased;sudden surge of water seepage path(The path between the point of sudden surge of water and the recharge aquifer)longer,instantaneous sudden surge flow rate is larger,surge phenomenon is more obvious,the length of the seepage path on its stable phase of the flow of the influence is not large,the stable flow tends to be consistent;the higher the initial head height,the higher the initial head height,the lower the instantaneous water pressure drop,the lower the instantaneous surge water flow with the increase in head height,and the higher the surge water flow at the time of stabilization.(4)According to the appropriate kinetic equations,the seepage path will be divided into three sections: aquifer section(Darcy region),fault zone section(Brinkman region),and coal column broken section(N-S region).Taking the permeability,dip angle,and width in the fault zone as the main control factors,three sections of the seepage path coupled sudden surge water numerical model were built.As the permeability of the fault zone increases,the water pressure drop and seepage velocity of the aquifer increase;the change of the dip angle of the fault zone has less effect on the water pressure in the aquifer;after the water flows through the aquifer section into the fault zone section,the flow velocity rises sharply to reach the peak and becomes stable,and the stable flow velocity increases with the increase of the dip angle of the fault zone;when the width of the fault zone increases,the seepage velocity in the fault area increases,and the head of the aquifer section is significantly lower than that of the fault When the width of the fault zone increases,the seepage velocity in the fault area increases,and the water head in the aquifer section is significantly lower than that in the fault zone.(5)According to the indoor test and simulation results,considering the dip angle of the fault,fault zone width,and permeability coefficient,and other parameters,this thesis amended the sudden surge of water instantaneous pore pressure distribution,instantaneous pore pressure influence radius of the calculation model and the calculation formula of the instantaneous sudden surge of water.The thesis has 61 diagrams,8 tables,and 72 references.