复杂应力路径下深部软弱夹层-岩体宏细观相互作用机制研究

A weak interlayer zone (WIZ) is a poor rock mass system with loose structure, weak mechanical properties, random distribution and strong extension due to the shear motion of rock masses under the action of tectonism, bringing many stability problems and geological hazards, especially representing a potential threat to the overall stability of rock masses with WIZ in deep underground engineering excavations. The macro-meso interaction mechanism of deep-buried WIZ and rock mass under complex loading and unloading stress paths is by far a crucial theoretical issue in rock and soil mechanics. In this study, a true-triaxial experimental system will be adopted as the main test apparatus. Based on the typical true triaxial loading tests, the true triaxial loading mechanical response of the loading angle and thickness of WIZ is revealed. A series of tests under different loading and loading stress paths, including the true triaxial stress path tests simulating the excavation-induced and cyclic loading-unloading stress paths via independent control of the three principal stresses, the interfacial repeated shear tests, as well as the acoustic emission，electron microscope scanning，CT meso-analysis and CT-MATLAB three-dimensional reconstruction simulation, would be carried out. Based on these results, we attempt to unearth the mysteries of the stress path dependence of WIZ and WIZ/rock interface strength and the macro-meso uncoordinated interaction mechanism between WIZ and rock mass under complex stress conditions. We then develop novel constitutive model and true-axial anisotropic strength criterion for WIZ and WIZ/rock interface, interpreting the stress path effect on the true triaxial strength and deformation of WIZ and WIZ/rock interface. The new constructive models would be a major advancement in realizing quantitative descriptions of the mechanical effects of stress path, thickness of WIZ, loading angle, interface morphology as well as the particle breakage and mechanical parameter evolution. Based on the extended finite element method, the new models will be verified by analyzing the stability of a typical deep underground cavern controlled by rock masses with WIZ. This study will provide theoretical basis for the analysis and prediction of the instability of deep underground projects controlled by rock masses with WIZ.

深部地下工程大规模开挖扰动应力路径下软弱夹层-岩体相互作用力学行为及破坏机制研究是目前岩土力学领域关注的重要科学课题。本项目首先基于典型真三轴加载试验，揭示软弱夹层产状和厚度的力学响应；通过独立控制真三向应力开展开挖扰动及循环加卸荷、循环剪切试验，辅助声发射-扫描电镜-微米CT细观分析手段及CT-MATLAB三维重构，针对性揭示软弱夹层和界面强度的应力路径相关性和软弱夹层-岩体非协调相互作用力学机制。基于此，构建软弱夹层及界面本构模型和真三轴各向异性强度准则；解译复杂开挖扰动应力路径对软弱夹层岩体真三轴强度和变形的影响程度，实现对界面形貌、产状、厚度力学效应以及颗粒破碎程度、强度参数损伤劣化的定量表征。基于扩展有限元平台，将新模型应用于典型深部地下洞室含软弱夹层岩体稳定性分析验证有效性。项目成果可为受软弱夹层影响的深部岩土工程围岩失稳破坏分析和预测提供理论依据。

深部地下工程大规模开挖扰动应力路径下软弱夹层岩体力学行为及破坏机制研究是目前岩土力学领域关注的重要科学课题。本项目研究贯穿了深部软弱夹层岩体应力赋存状态判据、软弱夹层岩体产状/厚度力学效应、软弱夹层-岩体的应力路径相关性、多尺度变形破坏力学机制与规律、力学模型以及现场实践验证等研究的全过程，总体上达到了预期目标。研究取得的代表性成果如下：①建立了考虑最大主应力值、岩石饱和单轴抗压强度、岩石完整性系数、地质强度指标、岩体纵波波速、垂直埋深、主要岩性、围岩级别的多因素深部软弱夹层岩体应力赋存状态数据驱动判据模型，结合实际工程的原始应力数据并与现有的地应力判别方法对比验证了模型准确率和普适性；②提出并总结了复杂扰动应力路径下软弱夹层的三轴试验方法，并揭示了复杂扰动应力路径下软弱夹层的卸荷（塑性）变形特征、强度特征、剪胀角、力学参数的宏细观裂化机制；③从试验和离散元模拟角度充分解译了深部软弱夹层-母岩非协调变形破坏过程和厚度/产状力学效应；④开发了考虑复杂应力路径影响的深部软弱夹层修正塑性功本构模型，模型可反映出软弱夹层的剪胀、剪缩、各项异性特征以及强度变形参数随修正塑性功的劣化过程；⑤诠译了软弱夹层岩体微震事件破裂机制的时空演化规律，并实现了受软弱夹层影响的大型地下洞室群灾害预警与分析。