Gong Sheng, Chen Lili, Chen Xingzhou, Li Zhenhan
School of Architecture and Civil Engineering, Xi'an University of Science and Technology, Xi'an, 710054, China.
Sci Rep. 2025 Aug 2;15(1):28285. doi: 10.1038/s41598-025-13761-2.
As tunnel engineering in western China advances deeper underground, it encounters increasing issues of high ground temperature and high water pressure. To study the mechanical properties of unloading sandstone under the combined effects of temperature and pore water pressure, triaxial unloading and reloading experiments were conducted on sandstone under different temperatures, pore water pressures, and confining pressures. The results showed: (1) The peak strength of unloading sandstone decreases with increasing temperature and pore water pressure. The elastic modulus of unloading sandstone increases with temperature but decreases with increasing pore water pressure. (2) The influence of pore water pressure on the unloading deformation of sandstone has a threshold. At low pore water pressure (1 MPa), temperature has little effect on the deformation of unloading sandstone. At medium to high pore water pressures (2, 3 MPa), temperature-induced unloading softening characteristics are obvious. (3) SEM images show that with increasing temperature, the number and width of microcracks in the rock increase. With increasing pore water pressure, rock cohesion decreases and friction angle increases; under 3 MPa water pore pressure, rock cohesion decreases by 24.8%. (4) The rock's energy storage capacity decreases with increasing temperature and pore water pressure. At high pore water pressure (3 MPa), the effect of temperature on the dissipation energy of sandstone is more significant. In addition, as the temperature rises, the proportion of elastic energy at the rock's peak increases, while the proportion of dissipation energy decreases.
随着中国西部隧道工程向地下更深层推进，高地温、高水压问题日益凸显。为研究温度和孔隙水压力共同作用下卸荷砂岩的力学特性，开展了不同温度、孔隙水压力和围压条件下砂岩的三轴卸荷再加载试验。结果表明：（1）卸荷砂岩的峰值强度随温度和孔隙水压力的升高而降低。卸荷砂岩的弹性模量随温度升高而增大，但随孔隙水压力升高而减小。（2）孔隙水压力对砂岩卸荷变形的影响存在阈值。在低孔隙水压力（1MPa）时，温度对卸荷砂岩变形影响较小。在中高孔隙水压力（2、3MPa）时，温度引起的卸荷软化特性明显。（3）扫描电镜图像显示，随温度升高，岩石内部微裂纹数量增多、宽度增大。随孔隙水压力升高，岩石黏聚力减小，内摩擦角增大；在3MPa孔隙水压力作用下，岩石黏聚力降低24.8%。（4）岩石储能能力随温度和孔隙水压力升高而降低。在高孔隙水压力（3MPa）时，温度对砂岩耗能的影响更为显著。此外，随着温度升高，岩石峰值处弹性能比例增大，耗能比例减小。
