Study On The Coupling Mechanism Of Multi-physical Fields And Early Warning Information Of Water Inrush From Fault Structure In Coal Seam Floor

Fengfeng mining area is a typical large-water mining area of North China type coal field in China.The Ordovician limestone aquifer with large water pressure is widely distributed at the bottom.With the continuous reduction of shallow coal resources,the buried depth of coal seams in some mines is gradually greater than 1000m,and the thickness of effective aquiclude between coal seam floor and aquifer is decreasing.The deep coal seam is usually in a complex geological environment with high ground stress,high confined water pressure and wide development of fault structures.The floor water inrush channel is gradually transformed from mining fracture to fault structure.Therefore,how to ensure the safety of mine production threatened by floor water inrush is one of the important scientific problems to be solved urgently.This thesis chooses Wutongzhuang mine in Fengfeng mining area as the study area.On the basis of fully collecting and sorting out the previous water inrush accident data,the similar material simulation test and numerical simulation method are used to reproduce the water inrush process of coal seam floor fracture structure.The variation law of different physical quantities of stope rock mass during the mining process of working face is studied,and the coupling mechanism of multi-physical field is clarified.Combined with the difference of response characteristics of each physical quantity before and after water inrush,the early warning information of water inrush is put forward.The research results are as follows:（1）On the basis of fully collecting and sorting the previous water inrush accident data of Wutongzhuang mine in Fengfeng mining area,the water inrush of floor fracture structure in 182201 working face is selected as a typical water inrush case.Based on the fluid-solid coupling theory,the similarity ratio is determined,and the water inrush process of the floor fracture structure is reproduced:with the continuous mining of the working face,mining cracks appear between the fault activation zone and the floor failure zone.When the width reaches 2mm,a water inrush channel is formed,and the water volume in the stope increases,and water inrush occurs.Determine the working face mining to about40cm,to focus on monitoring the physical changes in the moment.（2）Combined with the similar material simulation model,the numerical model is established by FLAC^3D simulation software.The evolution characteristics of stress field,displacement field and seepage field through the fault in the process of working face mining are studied:with the working face forward mining,the stress of floor strata experiences the change process of increase-steep rise-sudden drop;the floor strata produce upward displacement and gradually become stable;the water pressure on the rock mass near the floor of the working face increases steadily,and decreases slowly after reaching the extreme value.The deformation of the floor strata is more obviously affected by the stress;the correlation coefficient between the physical fields of the rock mass in the upper part of the fault is high,which indicates that the mining affects the underlying aquifer,and the displacement of the rock mass provides space for the upward flow of water along the fault.（3）Based on the similar material simulation test and numerical simulation results,the variation law of different physical quantities of water inrush position in the process of working face mining is analyzed respectively:when the working face is mined to35cm～45cm,the stress of the water inrush position of the floor rock layer decreases sharply,and there is a minimum peak value.The water pressure at the water inrush position through the fault falls in a cliff type.The variation of stress and water pressure on the location of water inrush in floor rock is more intense,which indicates that the response characteristics of each physical quantity in floor rock to water inrush are more obvious,and it is more suitable as the early warning information of water inrush in fracture structure.