Mechanical Properties of Hollow Sandstone Under Triaxial Compression and Hydraulic-Mechanical Loading
摘要
Water conveyance tunnels are subjected to significant internal water pressure, which impacts the lining and weakens the surrounding rock. This study investigates the mechanical response and failure characteristics of such tunnels using triaxial compression tests on hollow cylindrical sandstone specimens with mortar layers simulating tunnel linings under varying confining and internal water pressures. Results show that increasing confining pressure enhances peak strength, elastic modulus, and brittleness while altering failure modes. For specimens with a 20 mm hole diameter and no internal water pressure, increasing confining pressure from 6 to 12 MPa and 18 MPa raised peak strength by 25.91% and 32.47% and elastic modulus by 17.78% and 23.42%, respectively. Larger hole diameters significantly reduce mechanical performance due to stress concentration, whereas internal water pressure alleviates this weakening by modifying stress distribution. At a confining pressure of 6 MPa, the peak strength reduction for 20 mm specimens decreased from 21.41 to 13.67% and 0% as the P1/P2 ratio increased from 0 to 0.3 and 0.6, respectively. The mortar lining improves strength and promotes shear failure under low confining pressure, with stronger reinforcement under internal water pressure. Additionally, higher confining pressure and mortar lining increase axial peak strain, while higher internal water pressure and larger hole diameter reduce it.