Theoretical Study on Stress and Strain in Hydrostatic Compression of Jacketed Rock Specimens

抄録

When a weakly anisotropic rock specimen is subjected to hydrostatic compression, axial and circumferential strains are expected to be identical. However, differences are sometimes observed when the specimen is jacketed with a heat-shrink tube. This study theoretically examines whether the mismatch in elastic properties between the rock and jacket can explain this discrepancy. Assuming linear elasticity and interfacial slip, the stress and strain responses under hydrostatic compression were derived. The analysis shows that a stiffer jacket generates circumferential stress exceeding the applied confining pressure, reducing the pressure transmitted to the rock and causing smaller circumferential strain than axial strain. In contrast, a compliant jacket allows pressure transmission close to the applied pressure, resulting in nearly identical strains. These results highlight the importance of jacket stiffness in interpreting hydrostatic strain measurements.