盾构隧道接头渗水对其变形及内力的长期影响

Long-term influence of leakage at shield tunnel joint on its deformation and inner force

以上海地铁盾构隧道为工程实例,采用有限元软件建立了盾构隧道接头局部渗水模型,计算分析了不同边界条件下盾构隧道接头渗水对隧道变形及内力的影响。计算结果表明:若渗流程度和边界条件不同,则渗流达到稳定状态的时间不同,且进一步导致隧道周围土体孔压的消散程度、地表沉降、隧道变形和管片内力均存在明显差异;地表沉降、隧道直径变化量和管片内力随孔压的发展规律几乎一致;接头渗流会导致管片接缝处孔压明显低于周围土体的孔压,且渗流越严重孔压相差越大。研究表明,在接头渗水严重且没有外部水源补给的极端情况下,孔压、地表沉降、隧道椭圆化变形及管片内力会持续改变且变化幅度较大,尤其是弯矩的改变量非常显著,此种情况下,隧道长期渗水带来的危害最为显著。

Taking Shanghai subway tunnel as an example, a model of leakage at shield tunnel joint was established with the finite element software to investigate the deformation and inner force of the shield tunnel by considering different seepage boundaries. The results indicate that the distribution of pore pressure, ground settlement, deformation of tunnel and inner force all vary significantly with different seepage boundaries and permeability coefficients, and the duration reaching steady leakage are also different. The developments of surface settlement, tunnel diameter variation and internal force with the pore pressure are almost the same. The leakage at joint can result in a significant decrease of pore pressure around the tunnel joints, the more serious the leakage is, the larger the pore pressure difference is. In an extreme case of high - permeability of tunnel joints and no extra groundwater, the pore pressure, surface settlement, tunnel deformation, internal force, and bending moment will be in a continuous variation with significant amplitude, which may pose a severe threat on the safe operation of the subway.