| In the process of coal mining production,the main engineering rock mass excavated is coal rock and sandstone.In the long geological process,there are a lot of pores and fissures in the coal rock,while the sandstone is generally attached to the top and bottom of the coal seam.In the process of mining,the sandstone will produce secondary fissures or even cracks.These holes and fissures in coal rock and sandstone are the main channels of groundwater seepage.Therefore,it is of great significance to study the seepage characteristics of hole and fissure for the in-depth understanding of water seepage mechanism in underground mines.In view of the two main factors affecting the coal seepage: confining pressure and water pressure,a rock permeability analyzer is used to carry out seepage tests under different water pressure and confining pressure on coal rock and fractured sandstone,and the seepage flow under different loads is obtained.In order to further analyze the seepage movement and pore deformation law of internal cracks in coal and rock tests under different water pressure,the seepage model of coal and rock pores was established by using NMR scanning and image reconstruction technology.Then,with the help of COMSOL software,the two sides of the coal and rock are taken as the fixed boundary,and the upper boundary is subjected to 1?10MPa hydraulic pressure step-by-step loading respectively,to carry out the numerical simulation analysis on the seepage movement of the micro-fracture channel of the coal and rock.Influencing factors,based on the rough fracture interface based on barton ten standard contour line,established by using numerical simulation software COMSOL coarse single fracture seepage model,research work was carried out by different rough fracture seepage features,seepage flow velocity change in the process of monitoring,and through the cubic law of formal for permeability calculation,At the same time,the stress variation in the crack channel was observed.Through physical and numerical tests,the following research results have been obtained:(1)The seepage law of coal pore under confining pressure and water pressure is as follows: the water pressure is in the range of 1?4 MPa,the water pressure is constant,the confining pressure is increased step by step from 1?10 MPa,the seepage flow,seepage velocity and permeability are gradually decreasing.The curve law is divided into three stages:when the confining pressure is 1?4 MPa,it is a nonlinear stage;When the confining pressure is 4?8 MPa,it shows a linear stage.When the confining pressure is above 8 MPa,it shows a constant horizontal stage.When the confining pressure is in the range of 1?10 MPa and the confining pressure is constant,the water pressure increases step by step from 1?4 MPa,and the seepage flow,seepage velocity and permeability all increase gradually.When the confining pressure is lower than 4 MPa,the increasing trend is obvious.When the confining pressure is greater than 4 MPa,the increase of seepage flow,permeability velocity and permeability is small.(2)The seepage law of sandstone fractures under confining pressure and water pressure is as follows: the confining pressure is constant at all levels,and the seepage flow and permeability gradually increase when the water pressure increases.However,when the confining pressure is 1?2 MPa,the seepage flow and permeability increase greatly,and when the confining pressure is 3?10 MPa,the seepage flow and permeability increase steadily.When the confining pressure is 1?5 MPa,the seepage flow and permeability decrease rapidly.When the confining pressure is 5?10 MPa,the seepage flow and permeability decrease gently,presenting an approximate linear law.(3)The numerical simulation law of seepage velocity and seepage field in coal under the influence of water pressure is as follows: with the increase of water pressure,the average seepage velocity increases in a logarithmic trend;The maximum seepage velocity growth trend can be divided into three stages: the direct proportion stage with a large growth rate,the near horizontal stage and the direct proportion stage with a small growth rate.The stress field and seepage field influence each other,and the hydraulic coupling is the main factor that causes the change of seepage velocity.(4)The seepage law of fractures with different roughness is as follows: the maximum velocity and average velocity decrease with the increase of JRC value;Vortex field is generated in the flow through the rough fracture.The larger the JRC value is,the more disorganized the vortex circle is and the more irregular the shape of the vortex is.The permeability increases with the increase of JRC value in a logarithmic form.The variation trend of permeability is only related to roughness and has nothing to do with fracture opening.The research results provide reference for the seepage law of fractured rock mass. |
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