地下洞室开挖卸荷过程中,节理岩体的力学特性和裂纹扩展行为对工程的安全和稳定至关重要。本文以四川卡拉水电站地下厂房节理砂质板岩为研究对象,开展完整和非贯通节理砂质板岩三轴加卸载试验,分析了不同应力路径下砂质板岩力学与变形特性,探讨了不同强度准则描述砂质板岩加卸荷力学特性的适用性,并结合断裂力学探究其裂纹扩展机制。研究结果表明：(1)随着初始围压的增加,不同应力路径下试样破坏时的轴向应力和轴向应变均呈增加趋势。(2)与三轴加载试验相比,卸荷路径及节理均会使试样承载能力降低,升轴压卸围压和卸轴压卸围压时完整试样黏聚力c分别增加4.1%和减少30.4%,内摩擦角φ分别增大3.5%和7.3%,节理试样较完整试样黏聚力c分别降低32.9%和53%,内摩擦角φ分别降低2.2%和10%。(3)Mogi-Coulomb强度准则较Mohr-Coulomb和Drucker-Prager强度准则能更好地表征砂质板岩在加载和卸荷过程中的破坏强度特征。(4)在相同路径下,理论起裂角大小随围压的增加而递增,而双节理试样均大于完整试样。不同路径下试样的理论起裂角大致集中在55°～60°。

During the excavation and unloading of underground chambers, the mechanical characteristics and crack propagation behavior of jointed rock formations are vital for project safety and stability. In this study at the Karala Hydroelectric Station in Sichuan, we conducted comprehensive tests on non-penetrating jointed sandy shale under triaxial loading and unloading conditions. We analyzed the mechanical properties and deformation characteristics under different stress paths, explored the applicability of various strength criteria, and investigated crack propagation mechanisms using fracture mechanics. The research outcomes have yielded the following insights:(1) As initial confining pressure increases, axial stress and strain at failure show an upward trend under different stress paths.(2) Compared to triaxial loading, unloading and jointed samples decrease load-bearing capacity. Unloading from axial stress to confining pressure increases cohesion (c) by 4.1% and decreases it by 30.4% during unloading from confining pressure to axial stress. Internal friction angle (φ) increases by 3.5% and 7.3% during axial compression, while jointed samples show a decrease of 32.9% and 53% in cohesion (c) and a decrease of 2.2% and 10% in internal friction angle (φ).(3) In terms of characterizing the strength properties of sandy shale throughout the loading and unloading process, the Mogi-Coulomb strength criterion outperformed both the Mohr-Coulomb and Drucker-Prager criteria. (4) The theoretical critical angle increases with confining pressure, and biconjoint samples exhibit higher values than intact ones. The theoretical critical angles range from 55° to 60° under different loading paths.

TU45

国家自然科学基金(U1965109)；湖北省自然科学基金(2022CFB345)