Study on the Deformation Characteristics of Fractured Basalt Under Coupling of Three-Dimensional Stress and Water Pressure Cycling

The seepage-stress coupling of fractured rock masses is a physical, chemical and mechanical process that depends strongly on the lithological conditions, structural state, initial stress level and stress path for the hydraulic coupling during water storage. A newly developed true triaxial hydraulic coupling test system named HMTS-1200 was used to carry out triaxial hydromechanical coupling deformation tests on fractured basalt under water pressure along a cyclic loading and unloading path. The following test results were obtained. During cyclic water pressure loading and unloading, the additional axial deformation exhibits the characteristic fluctuations of compression-expansion-compression, whereas the lateral deformation exhibits the characteristic fluctuations of expansion-compression-expansion. Under hydraulic-mechanical coupling, the coupling of the axial pressure and the water pressure is noticeable. The lower the axial pressure is, the more noticeable the additional specimen deformation is. The deformation modulus of the fractured basalt under triaxial stress-hydraulic pressure coupling depends strongly on the loading-unloading of the water pressure and the confining pressure. The deformation modulus is logarithmic in the number of cycles and linear in the water pressure. The abovementioned test results serve as an important reference for the study of hydraulic coupling characteristics of and time effects on bank rock mass deformation parameters during reservoir operation.

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