盾构隧道管片接缝气密性模拟方法与影响因素分析
Simulation method for gas tightness of segment joints of shield tunnels and analysis of influencing factors
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摘要: 盾构隧道穿越含气地层时,施工对地层的扰动易引发气体泄漏,气体易由盾构管片接缝处进入隧道内部,极易引发爆炸等灾害。依托穿越长江高压含气地层的苏通GIL综合管廊工程,较系统地研究了影响盾构管片接缝面气体泄漏的主要因素,并提出对应改进措施。通过接缝室内模型试验,分析了气压加载下接缝面气体泄漏的全过程,从而揭示了气体在不同泄漏阶段影响接缝面气密性的主要因素。建立了接缝数值模拟模型,研究了气压加载下,接缝面张开量、管片表面粗糙程度对接缝气密性能的影响。基于粗糙表面密封间隙气体流动的PC模型,建立了盾构管片接缝处气体泄漏率理论计算方法,并将计算结果与模型试验结果进行对比,证实了理论计算方法的可行性与适用性。最后,结合模型试验与理论计算方法,提出了降低接缝气体泄漏率的措施。Abstract: When a shield tunnel passes through a gas-bearing stratum, the disturbance of construction to the stratum is easy to cause gas leakage, and gas tends to enter the tunnel through the joint of shield tube, which is easy to cause explosion and other disasters. Based on the Sutong GIL integrated pipe gallery project which crosses the high-pressure gas-bearing strata in the Yangtze River, the main factors affecting gas leakage on the joint surface of shield tunneling tube are studied, and the corresponding improvement measures are proposed. The whole process of the gas leakage in the joint surface under pressure loading is analyzed through the joint model tests, and the main factors affecting the gas tightness of the joint surface at different stages of gas leakage are revealed. A numerical simulation model for joints is established to study the effects of the opening of the joint surface and the roughness of the pipe surface on the gas tightness performance of joints under pressure loading. Based on the PC model for gas flow in seal gap of rough surface, the theoretical method for gas leakage rate at the joint of shield tube is established, and the results are compared with those of model tests, which proves the feasibility and applicability of the theoretical method. Finally, by combining the model tests and the theoretical method, the measures to reduce the gas leakage rate of joints are put forward.