Study On The Mechanism Of Water Inrush From Transfixion Faults Floor Of The Lower Group Coal Above The Confined Water Mining In Weibei

In recent years,with the large-scale development of coal resources in North China,the mining level has shifted to the stage of deep and lower group coal mining,the hazards of confined water of Ordovician limestone from coal measures floor is becoming more and more serious,and structural floor water-inrush accidents occur frequently.For example,the through fault structure of the main coal seam floor commonly existent in Weibei mining area,how to effectively prevent and control the water-inrush disaster of the through fault floor is the focus of disaster prevention of the mine.Therefore,revealing the mechanism of water-inrush from through faults floor of the lower group coal above the confined water mining in Weibei coalfield is the basis and key to realize "water preserving mining" on the floor,and is an important scientific problem that needs to be solved urgently at present.Based on this,this paper takes the No.5 coal seam floor of Dongjiahe Coal Mine as the research object,using theoretical analysis,numerical simulation and engineering practice to conduct in-depth discussions on the mining failure characteristics and catastrophic law of the through fault floor,and draws the following conclusions:(1)Based on the analysis of hydrogeology and previous water-inrush data in Weibei mining area,the fault types of Weibei mining area are classified,and the process of fault activation and the main factors that affecting activation and water conduction of floor faults is summarized and analyzed.Such as mine pressure,confined water pressure,fault type,fault dip angle and floor lithologic combination mode,etc.Under the combined action of these factors,whether the fault is activated is the key to determine whether the floor can inrush water(2)Comprehensively considering the influence of roof 'arch' caving gangue pressure and confined water pressure on floor stress field in working face goaf,the mechanical model of additional stress of floor before and after full mining is established,combined with elastic-plastic mechanics,the mechanical distribution state of floor rock mass and theexpressions of vertical stress,horizontal stress and shear stress before and after full mining are derived,and according to the strength failure criterion,the plastic failure range of floor rock mass and fault is given,combined with the actual geomechanical parameters in the field,the structural failure characteristics of floor rock mass under different lithologic combinations and fault dip angles are analyzed.At the same time,combined with the limit failure theory,the mechanical model of floor water-inrush induced by confined water in fault zone is established,and the mechanical expression between confined water pressure and the width of remaining waterproof coal pillar in limit equilibrium state is deduced.The analytical solution of the limit width of waterproof coal pillar is given,which provides a theoretical basis for the setting of waterproof coal pillar in the working face.(3)By using FLAC3D finite difference software and taking the second horizontal and third mining area of No.5 coal mine in Dongjiahe Coal Mine as the engineering geological background,the fluid-solid coupling numerical calculation model of through fault floor is established,and the whole process of "fault activation? fracture expansion?water-inrush channel forming?floor water-inrush" is analyzed and compared under different fault dip angles.Revealed mining failure law of through fault floor,the law of fault activation and water diversion,the evolution law of the stress field and the displacement field and the characteristics of seepage(4)Based on the actual mining conditions of 23503 working face in Dongjiahe Coal Mine,the minimum theoretical width of waterproof coal pillar is given.Combining with the deformation and failure of the floor under two working conditions of coal pillar width and the law of fault activation,the safety width of waterproof coal pillar is determined.The safety threshold value is better than the experience value of 'Coal Mine Safety Regulation',which provides reasonable data for the location of new open-off cut in the working face.According to the research results of this paper,the implementation scheme of grouting transformation of floor under working face and new open-off cut is put forward,and the safe mining of mining face is realized,which provides engineering reference and practical experience for water disaster prevention and control of structural floor under similar conditions in Weibei mining area.