Study On Solid-liquid Coupling Mechanism Of Water-conducting Fracture Zone Development Under Shallow-buried Deep And Strong Mining Disturbance

Coal resources in North Shaanxi Energy Base is the largest coal field,with shallow burial depth,large thickness and good coal quality,in China and one of the most important energy and chemical bases in China,which plays a very important role in local economic development.However,northern Shaanxi is located in arid and semi-arid areas,lacking surface water resources and fragile ecological environment.The phreatic aquifer of the Quaternary Salawusu Formation is the main source of water supply for local people,livestock and ecological vegetation.And when it's damaged,it's hard to recover.Therefore,it is of great significance to study the solid-liquid coupling mechanism of water-conducting fracture zone development under the interaction of overlying strata mechanical properties and phreatic hydraulic properties of Salawusu aquifer after strong mining disturbance in Shenfu mining area.Taking Hanglaiwan Coal Mine as an engineering background,this paper studies the development law of upward and downward cracks in overburden strata under the coupling action of mining stress field and seepage field,and the solid-liquid coupling mechanism of the development of water-conducting fracture zone by means of theoretical analysis,numerical simulation and similar material simulation.The main conclusions are as follows:(1)Surface morphology and aquifer structure have important influence on the development of downward fissures.Longitudinal fissures at the bottom of the valley are inverted wedge"and those at the slope of the valley are"wedge".The development degree of fissures in the region of gully and plain beams is relatively small.The thicker the aquifer,the greater the erosion intensity of the aquifer,and the deeper and wider the concave downward fissure zone in the middle of the goaf.The interaction between water and rock mass in downward fissures is mainly manifested by the erosion of water body to downward fissures and the erosion of rock mass by water body in the middle of goaf.(2)The width of working face,the lithologic combination characteristics of overburden and topography have important influence on the development of upstream fissures.The farther the key seam is from the roof of coal seam,the smaller the height of upstream crack development and the wider the influence scope.The wider the width of working face,the higher the height of upstream fracture development and the wider the scope.The height of upstream fissures is the highest at the location of surface valleys.The height of upstream fissures at the location of surface valleys is the highest affected by various factors.The more developed tension fissures are at the boundary of goaf,the better the fissure conductivity is,and the easier to form water diversion channels.In the upper part of the goaf,the rock mass is compacted,and the upward cracks are poor in penetration,so it is not easy to form a smooth channel for water diversion.(3)The coupling mechanism of water and rock mass at different locations in water-conducting fracture zone is different.Upper and downward fissures are conductive,forming water-conducting fissure zones.The fissures on both sides of goaf are well developed,which is the dominant channel for water-conducting.The interaction between water body and rock mass is mainly erosion.The cracks in the middle of the goaf are closed and water body is gathered.Under the action of overburden pressure,the stored water body intrudes into the rock mass and forms erosion damage to the rock mass.