花岗岩残积土地基深开挖下运营地铁盾构隧道变形规律研究

Deep excavation is performed inevitably near to metro shield tunnel in the utilization of urban underground space, which causes unfavorable effects on the safety of tunnel. For structural granite residual soil, limitations of understanding its mechanics of structural granite residual soil under unloading condition and the corresponding analysis of deformation of tunnel structure contributes to the large deformation. In order to understand the deformation mechanism of shield tunnels in granite residual soil, in-situ and laboratory tests on different unloading stress paths are combined and carried out to investigate the unloading behavior. Utilizing the experimental results, the relationship between structural damage and strength or stiffness is clarified and a method of evaluating the damage is developed based on shear modulus. The mechanical model of unloading arch is established based on the discovered evolution of unloading arch. The method of the calculation of superimposed load of tunnel is then proposed. The model of contact coupling mechanism between shield tunnel and soil is also developed considering shield tunnel shearing effect and segment rings longitudinal joint. The model is used to study the behavior of shield tunnel, and the result is further verified by the field results. Research of this project will provide scientific and technical support for the design of the utilization of urban underground space with structural granite residual soil.

城市地下空间开发不可避免地会在运营地铁盾构隧道周边从事深基坑开挖，对隧道结构安全产生诸多不利影响。针对花岗岩残积土地区，开挖扰动下结构性花岗岩残积土工程特性认识的局限性及相应条件下地铁盾构隧道变形计算方法的欠合理性，是造成这类地区地铁隧道变形超标的重要原因。针对运营地铁盾构隧道变形问题，将现场测试和室内试验有机结合，研究开挖卸荷应力路径下花岗岩残积土的强度、变形特性发展规律，阐明结构性扰动程度与强度、刚度之间的内在联系，提出基于剪切模量的结构性损伤评价方法；在此基础上揭示地基土中卸荷拱发展规律，提出卸荷拱力学模型，构建既有盾构隧道附加荷载计算方法，考虑隧道-土体接触变形机制和盾构管片环向、纵向结构特性，提出盾构隧道-土体相互作用力学模型，揭示运营地铁盾构隧道的变形规律，通过实测数据校核和完善计算模型及参数取值方法。研究成果将为城市地下空间开发安全保障提供科学和技术支撑。

本项目以华南、东南地区城市地下空间开发环境下运营地铁盾构隧道保护问题为工程背景，针对开挖扰动下花岗岩残积土中隧道变形机理这一难题，展开相关研究。基于现场测试和室内试验，同时获取了花岗岩残积土的强度和剪切波速测试结果，研究了不同应力状态、应力路径下花岗岩残积土结构性演变规律，构建了基于小应变剪切模量的结构性损伤评价方法；探明了基坑开挖引起的坑周土体的变形规律，研究了卸载量与隧道隆起变形的发展规律以及隧道横断面的变形模式；提出了考虑螺栓和混凝土管片的弹塑性行为的铁木辛柯梁抗弯刚度和环缝张开量的计算方法，提出了三阶段的铁木辛柯梁剪切刚度和环缝错台量的计算方法；建立了考虑地层抗力非连续的纵向和环向隧道-地层相互作用理论模型；考虑盾构隧道的服役性能，通过安全系数来量化盾构隧道的正常使用极限状态，此外还提出了一种简化分析方法，该方法不需要进行复杂公式的求解，主要通过查表法就可以直接获得隧道纵向的变形。