Study On Seepage Characteristies Of Sandstone Affected By Fracture Surface Roughness And Fracture Width

The exploitation of underground mineral resources and other projects often face problems such as water inrush and seepage of coal seam roof(sandstone),which is closely related to the seepage characteristics of fluid in sandstone.The accurate characterization of the fractured surface morphology of sandstone is of great significance to reveal the seepage law of sandstone.Based on the ideal cubic law and the seepage test of sandstone fractures,the influence mechanism of fracture surface roughness and fracture width on seepage characteristics of sandstone is studied by maturing the surface roughness and opening width of sandstone specimen model.The results show that the surface roughness of sandstone fractures can be characterized by three-dimensional fractal dimension D and three-dimensional surface height deviation.The larger the surface roughness is,the larger the surface height deviation is,and the 3D fractal dimension D approaches 3.For the same rough fracture,the fracture seepage flow rate increase exponentially with the increase of the fracture opening width,and show obvious nonlinear characteristics.With the same fracture opening width,the seepage flow of the sandstone specimen is affected by the surface roughness of the fracture,and the surface roughness of the fracture is negatively correlated with the flow rate of the fracture seepage,The difference of the seepage flow in the low fracture width stage(50 ?m?175 ?m)is not obvious,The difference of the seepage flow in the high fracture width stage(175 ?m?300?m)is obvious;With the increase of the width of the fracture,the effect of the fracture surface roughness on the flow rate of the fracture is reduced.Through the dimension analysis method,the cubic law is improved,and the rough fractured flow model with 3D fractal dimension D is established,and there is a good agreement with the seepage law of sandstone fracture,model is more reasonable.