考虑高应力卸荷围岩-结构面耦合作用机制的洞室块体稳定性研究

For underground caverns in high geostress region, the excavation unloading will cause disturbance to the stress filed, thus leading to the changes of mechanical characteristics of structural planes. During this process, the forces of surrounding rock imposed on blocks become a significant factor influencing the stability of blocks. However, traditional rigid limit equilibrium calculation method used for block stability analysis cannot take into account the interaction between surrounding rock and blocks. In view of this, this project aims to solve the surrounding rock safety issue induced by block failure during the excavation process of large-scale underground caverns. By conducting comprehensive research approaches including laboratory tests on structural planes, theoretical analysis and numerical simulation, this project plans to study the mechanical characteristics of structural planes under high stress unloading condition, to establish the constitutive model and realize numerical simulation, to develop non-linear numerical method for analyzing the loading and unloading mechanical behavior of structural planes under high stress condition, to reveal the coupling mechanism of surrounding rock and structural planes during high stress unloading process. On this basis, by incorporating element reconstruction-element aggregation technique, block theory and the above mentioned non-linear numerical method, this project plans to distinguish key blocks considering the contact state and stress influences of structural planes, to expound its failure mode, to propose stability analysis method for cavern blocks considering the influences of high stress excavation unloading. It will provide theoretical basis and application examples for the stability control and reinforcement optimization of surrounding rock in high stress condition.

高地应力区地下洞室开挖卸荷引起的扰动应力场将驱使结构面力学特性发生变化，在这一过程中围岩作用力成为影响块体稳定的重要因素，而传统的块体稳定刚体极限平衡计算方法尚无法考虑围岩与块体的相互作用。鉴于此，针对高地应力区大型地下洞室开挖过程中块体失稳诱发的围岩安全问题，本项目拟采用室内结构面试验、理论分析与数值模拟相结合的综合研究方法，分析在高应力卸荷作用下结构面的力学特征，建立其本构模型并实现数值模拟，发展描述高应力条件下结构面加卸载力学行为的非线性数值分析方法，揭示高应力卸荷过程中围岩与结构面的耦合作用机制。在此基础上，融合单元重构-聚合技术、块体理论与所发展的非线性数值分析方法，实现考虑结构面接触状态和应力影响的关键块体判别，探讨其失稳模式，提出考虑高应力卸荷作用的洞室块体稳定性分析方法，为高应力环境下洞室的围岩稳定控制、加固设计优化等提供理论依据和应用基础。

对有厚度天然结构面开展法向和切向加卸载试验，揭示了具有岩屑充填并夹少量泥的有厚度天然结构面在复杂应力条件下的法向和切向力学特性及演化规律，建立了有厚度天然结构面法向循环加卸载本构关系。其次，将上述本构关系嵌入通用软件，研究了洞室开挖卸荷过程中的围岩与结构面的作用模式，并进一步揭示了对应于每种作用模式的围岩-结构面耦合作用机制。然后，在已提出的块体识别方法基础上，进一步提出了基于数值分析的岩石块体稳定性评价一般性方法，该方法能够考虑初始地应力、围岩变形和非滑面抗剪性能对块体稳定性影响，且在一定条件下，分析结果可与刚体极限平衡法结果基本等同。最后，将所提方法应用于实际工程，对其应用效果进行了评价。本项目研究了复杂应力条件下结构面的加卸载力学特性，提出了相应力学模型；揭示了洞室开挖卸荷过程中的围岩-结构面耦合作用机制；在已提出的岩石块体识别方法基础上，进一步提出岩石块体稳定性评价一般性方法，构成一套有关岩石块体的“识别-可动性判别-运动形式确定-稳定性评价-加固分析”的完整方法体系，总体平行于当前块体力学分析常用方法(如块体理论)，为研究块体在各种复杂条件下的稳定性演化提供了新的实现思路。