大跨度地下洞库节理围岩变形演化机理及支护设计理论研究

The stability analysis of underground excavations is critically important for the underground storage cavern design. Due to the adoptions of the large span and high wall, the design methods of the large span rock caverns should be revised as none of them could fully cover the complex construction conditions. This project aims to use the laboratory model tests, analytical studies, and numerical simulations to investigate the ground reactions of the surrounding rock masses and the performances of the reinforcement system, especially for the water-sealed oil storage caverns. The objectives include (1) to investigate and derive the bond-slip model of the rockbolt element with consideration of damage caused by cycle loadings. Parameter studies of the mechanical properties of mortar, loading history, borehole sizes are going to be carried out to understand their contributions to the bond-slip model of a rockbolt element; (2) to evaluate the failure modes of the local stability problems during sequential excavations, and explore the relationship between the possible loading acting on the rockbolt and the geometry of the unstable blocks under different geological condition and sequential excavation designs based on the results of numerical parameter studies; (3) to investigate the influence of seepage field on the natural arching effects with considerations of different geological condition and excavation processes, and examine the reinforce efforts of an artificial arch by comparing the results of natural arching. The key deliverables of this project will contribute to the design and construction guidelines for large underground rock cavern project.

利用我国优势地质条件，合理开发地下空间，建设能源储备基地，保证地下能源基地长期安全稳定运营是有效提高我国能源储备规模、保障国家能源安全的重要举措。现行设计规范并不能完全适合大跨度地下洞库无衬砌、大跨度、高边墙等特点。本项目拟采用室内试验、理论分析和数值模拟等多种研究手段，探索加卸载对锚杆单元粘结强度和刚度的影响，建立含循环损伤的粘结-滑移模型；揭示渗流-地应力耦合作用下节理围岩局部失稳和变形演化机理，探索不同节理性质、边界荷载以及洞库开挖设计对围岩局部稳定性和隧道渗水量的影响，建立地下洞库围岩失稳块体支护设计理论；分析渗流-地应力耦合作用下围岩压力拱效应空间形态和人工压力拱对节理围岩的加固效率，最终建立地下洞库压力拱的围岩加固设计理论。项目成果对揭示围岩-支护相互作用机理，充分利用围岩自承力，完善地下能源储库的施工开挖和支护设计具有明显的经济和社会效益。

利用我国优势地质条件，合理开发地下空间，建设能源储备基地，保证地下能源基地长期安全稳定运营是有效提高我国能源储备规模、保障国家能源安全的重要举措。本项目拟对大跨度地下洞库节理围岩变形演化机理及支护设计进行研究，通过开展锚固单元剪切试验与数值模拟，揭示了不同法向边界条件对锚杆单元粘结强度和刚度的影响规律，提出了DDA中多类离散锚固单元的粘结-滑移模型；引入能量吸收锚杆的锚固单元，解决了不同类型锚杆的相互协作及其与节理岩体的相互作用问题；结合理论推导与数值模拟研究渗透压力下地下洞库围岩的密闭性问题，揭示了流力耦合作用下节理围岩局部失稳和变形演化机理，提出基于衬砌内外渗透压力比R的解析模型，结合引水隧洞监测数据，分析了隧洞建设全周期内渗透比R的演化规律，并用于长期稳定性预测；利用理论推导与数值实验相结合的方式分析地下围岩压力拱效应空间形态，揭示人工压力拱对节理围岩的加固效率，建立了能量吸收锚固等效锚固岩体理论。以上为充分利用围岩自承力、完善地下能源储库的施工开挖和支护设计提供理论与科学依据。