基坑开挖诱发邻近盾构隧道周边围岩变形演化机理及处治技术的能耗分析方法研究

The deformation of liner structure for existing shield tunnels induced by adjacent pit excavation, would cause negative effects on the normal use of the tunnels and the operation safety of subway. The deformation of surrounding rock which induced by pit excavation would transmit around the rock mass of the adjacent existing tunnels. Moreover, the imperfect contact between the liner and the rock mass results from this transmission is the main reason of the liner deformation. The study of the deformation occurrence mechanism for surrounding rock around the pit and the influence of the deformation on the adjacent tunnel structure are issues with high engineering significance. Combining the advantages of energy analysis theory and variational method, the energy consuming model of the surrounding rock deformation of a shield tunnel induced by adjacent pit excavation is constructed in this issue. Based on the system minimum energy consumption principle, the failure mode and internal dissipation of energy distribution characteristic for the surrounding rock of the shield tunnel are obtained. Furthermore, the occurrence mechanism and transfer law of the surrounding rock deformation are illustrated. By studying the interaction between the surrounding rock and tunnel structure, segment crack mechanism and the integral deformation law of tunnel are revealed. Besides, corresponding treating measures are proposed. Finally, the centrifugal model experiment and numerical simulation are used to verify the theoretical calculating results. The research results can provide theoretical basis for stability evaluation of rock mass during the pit excavation and the prevention of deformation for adjacent tunnel.

基坑开挖有可能导致邻近既有盾构隧道衬砌结构发生变形进而对隧道的正常使用和地铁的运营安全造成不利影响。基坑开挖诱发的围岩变形在邻近隧道周边进行传递，导致衬砌与围岩发生不良接触，是造成衬砌结构变形的主要原因。因此，研究基坑周边围岩变形的发生和传递机理及其对邻近隧道结构的影响具有重要意义。本课题通过融合能量法和变分理论的优点，建立起基坑开挖诱发邻近盾构隧道周边围岩变形破坏的能量计算模型，基于系统耗能最小原理，获得隧道结构周边围岩破坏模式和内部耗散能分布特征，进而阐明基坑开挖诱发邻近盾构隧道周边围岩变形的发生机理和传递规律。在此基础上，通过分析围岩与隧道结构的交互作用，揭示了管片的开裂机理和隧道的整体变形规律，并提出了相应的处治措施，最后采用离心模型试验和数值模拟技术对理论计算结果进行验证。研究成果可以为基坑开挖过程中周边围岩的稳定性评估和邻近既有隧道变形破坏防治提供理论依据。

本课题采用极限分析上限定理和变分理论，结合模型试验和数值模拟技术对基坑开挖诱发邻近既有盾构隧道管片周边围岩松动变形特征以及由此导致的盾构隧道管片损伤演变规律开展研究，完成了预期研究目标，取得了预期的研究成果。主要研究成果如下：.(1) 建立了基坑开挖诱发邻近盾构隧道周边围岩变形破坏的能量法分析模型，推导了基坑开挖诱发邻近既有盾构隧道管片周边围岩松动变形曲线的解析方程，揭示了基坑开挖诱发邻近盾构隧道周边围岩变形的发生机理和极限状态下围岩的破坏模式。.(2) 构建了基坑开挖诱发下卧既有盾构隧道变形的有限元模型，获得了基坑开挖诱发下卧既有盾构隧道上浮变形特征和管片损伤演变规律，提出了防止基坑开挖诱发下卧隧道上浮和管片变形的有效方法。.(3) 构建了基坑支护结构地连墙成槽施工过程中槽壁的离散型三维破坏机制，提出了地连墙槽壁稳定性的非线性能耗分析方法，对复杂因素耦合作用下地连墙槽壁的稳定性进行了定量评估。.(4) 建立了新建地铁下穿既有建筑物桩基过程中诱发桩端持力层冲切破坏的非线性能耗分析模型，推导了桩端持力层冲切破坏面和对应的持力层极限承载力解析表达式，获得了桩端持力层的冲切破坏范围和桩端承载力极限值。.(5) 推导了在既有线路两侧深大基坑零距离开挖诱发既有隧道竖向变形的解析解，提出了新建基坑支护结构的优化设计方案并将研究成果应用于深圳市轨道交通13号线二期工程公明广场站下穿既有的6号线工程。.(6) 研发了基于粒子图像测速技术(PIV)技术的缩尺模型试验系统，通过对浅埋暗挖施工诱发的地层变形进行模型试验，获得了暗挖施工扰动诱发地层变形的演变规律。.(7) 课题执行期内获得中国公路学会科学技术奖一等奖1项，发表和录用论文15篇，其中SCI收录论文7篇，EI收录论文4篇，ESI热点论文1篇，授权实用新型专利3项，申请发明专利1项。