Simulation Experiment Research On The Developing Law And Seepage Characteristics Of Water-conducting Fracture Zone In Xiaobaodang No.1 Mine

Water-conducting fracture zone can be formed in the overlying rock as a result of underground mining of coal seams.As a primary pathway for mine water discharging and water bursting in mine,it is closely associated with the safe production of coal mines.Currently,Xiaobaodang No.1 Mine is under development,thus,the developing law of the mining-induced water-conducting fracture zone remains to be studied.Moreover,the developing law and seepage characteristics of the water-conducting fracture zone induced by the mining of 2-2 coal seam are of great reference values for the subsequent prediction and prevention of water hazards in mining areas.To this end,taking Xiaobaodang No.1 Mine in the Yushen mining area,northern Shaanxi,as the research object,the developing law and seepage characteristics of the water-conducting fracture zone induced in the area were studied in this paper through penetration test,mercury intrusion test,similar material simulation experiment,and numerical simulation experiment.As can be observed in the similar material simulation of 2-2 coal mining process,developed fractures in the overlying strata are still,dynamically changed under the stress impact.Specifically,some fractures in the middle of the overlying strata were reduced in width or closed under the impact of extrusion stress,while other fractures on both sides of the overlying strata were increased in width under the effect of persistent tension.In general,stress concentrations can be found in the overlying strata at all stages of the advance of the face together with small stress fluctuations at positions outside the advance of the face.Besides,compared with its stress variation,variations in the seepage field of the overlying strata show some hysteresis in terms of time.With the proceeding of mining of the coal seam,the height of the water-conducting fracture zone was presented in an obvious arch over morphology,indicating a stepwise increase.When the face was advanced by 225m,the height of the water-conducting fracture zone was developed to 175.7 m.After that,the height no longer increases with the advance of the face.In consequence,it failed to conduct primary impermeable layers of the red soil layer of Baode Formation in the mine area.Although the water-conducting fracture zone was not connected to primary impermeable layers under the mining of 2-2 mine,micro-fractures produced on the impermeable layer led to the phreatic water in the Sarawusu Formation breaks the red soil layer and penetrates downward.However,leakage was locally found in the red soil layer that is deemed as the impermeable layer of the Baode Formation.With a small amount of seepage,it can be observed that a relatively complete waterproof property is reserved as a whole.