Experimental Study On Seepage Characteristics Of Rough Fracture Rock Under High Confining Pressure

Hydraulic behavior in fractured rock has an important effect on geotechnical engineering,such as dam foundations,oil and gas exploitation,nuclear/radioactive waste repositories,geothermal resources exploitation,as well as underground space utilization.Seepage characteristics,seepage analysis and control of fractured rock are essential for engineering design and performance assessment.The traditional study on seepage analysis in fractured rock is cubic law based on parallel plate model.Due to the coupling environment and the coupling of rock deformation,fluid flow has nonlinear characteristics in the in fractured rock and the application of cubic law was limited.In this thesis,this study aims to investigate the nonlinear flow characteristics with fractured rock.So the author proposed to represent permeability evolution of fractured rock with fracture surface morphology and apertures distribution,and researched the granite nonlinear flow characteristics with theory and hydro-mechanical experiments.Analyzed the results,main conclusions are listed as follows:(1)Based on the High-precision 3D Laser Scanning Technique,rough fracture surface morphology and initial apertures distribution were studied.The results show that the asperity of a rough surface submits to the normal distribution.(2)Based on the distribution of initial aperture.A hydraulic aperture model and critical Reynolds number model under normal stress are then proposed.These models reveal the relationships between surface geometries,aperture distribution,hydraulic aperture and critical Reynolds number in the deformation process,and the rationality of the model are verified.(3)The nonlinear fluid flow tests were performed using granite fractures with different roughness,apertures and normal loadings.The results indicate that pressure gradient versus flow rate displays nonlinearity,and the experimental results are well fitted with the Forchheimer equation.Moreover,as the normal stress loaded,the hydraulic aperture and the critical Reynolds number decrease gradually with normal load.