Experimental Study On The Coupling Characteristics Of Micro-fracture Stress And Seepage In Deep Wells

TThe overall mining mode of coal mine in China is expanding to the deep,and the high seepage pressure and ground stress in the deep cause the change of the strength and permeability of rock mass significantly,which seriously affects the stability of surrounding rock mass in deep Wells.At present,scholars at home and abroad have carried out some researches on the stress-seepage coupling law of the fracture,but few experiments can make the fracture under the triaxial stress state,simulate the seepage characteristics of the fracture under the real deep well environment through high inlet pressure,and monitor the water pressure on the surface of the fracture in real time.Therefore,it is necessary to study the stress-seepage coupling mechanism of deep well sandstone.Based on laboratory test,theoretical analysis and numerical simulation,and from the perspective of roughness and openness,this paper conducts an in-depth study on the stress-percolation coupling characteristics of micro-fractures in deep sandstone,providing a theoretical basis for controlling the water seepage problem caused by micro-fractures in deep surrounding rocks.The research results of this paper are as follows:(1)Based on the surface morphology and stress-percolation coupling characteristics of rock mass fractures,a percolation mathematical model of the rock mass micro-fractures is established,and the stress-percolation coupling mechanism of the micro-fractures is summarized and deduced with consideration of the degree of opening and roughness.(2)The optimum ratio of similar sandstone materials was optimized by introducing chlorinated paraffin and silicone oil.The application of the thin film pressure sensor is studied,and it is reasonably arranged in the similar model of micro-fissure sandstone,and the data of micro-fissure surface water pressure is collected and treated dynamically and accurately.(3)Microcracks using triaxial stress seepage mechanism model test system,with different roughness(JRC)and the opening of the microcracks(b)can be detected sandstone stress and seepage coupling experiment research,get different confining pressure(σ),under the action of seepage water pressure of the micro cracks on the surface of water pressure(P0)change rule and law of seepage flow,and carries on the sensitivity analysis of various factors,sensitivity and weak:P0>JRC>b>σ.Based on the experimental data,the nonlinear flow behavior of microfracture seepage is studied by combining Forchheimer law and Izbash law,and the Reynolds number critical value of microfracture flow is discussed.(4)Based on laboratory tests,The Abaqus numerical simulation software is used to study the variation law of water pressure on the surface of micro fractures under the influence of different seepage pressure,and the comparison and conclusion based on the experimental data show that the approximate relationship between seepage pressure and attenuation water pressure at each measuring point in the fracture conforms to the quadratic polynomial relation.On the basis of the stress-percolation coupling mechanism of the micro-fracture,the expansion law of the micro-fracture is studied and summarized as the stress accumulation stage and the micro-fracture stable expansion stage.