盾构隧道局部长期渗水对隧道变形及地表沉降的影响分析

研究表明，盾构隧道长期渗水会造成地表及隧道严重沉降。针对盾构隧道局部渗流难以模拟的现状，首先提出了一种既符合盾构隧道刚度要求又能实现局部接头渗水的计算方法；在稳定渗流状态对应的相同渗流量的前提下，对比分析了管片在不同接头渗水条件下隧道周围土体孔压分布、地表和隧道沉降以及隧道变形规律。分析结果表明，盾构隧道渗水接头的位置不同，孔压分布、地表和隧道沉降以及隧道的变形均有明显差异；接头位置越靠近隧道底部，渗水导致的孔压减小越显著，造成的地表及隧道沉降越显著。接头渗水不但会使隧道发生横向椭圆化变形，还会引起隧道左右两侧受力不平衡，从而造成隧道水平侧移。通过对比表明，采用接头渗水和传统的衬砌均质渗水得到的孔压分布、沉降及隧道变形规律均有显著不同；不考虑隧道局部渗水特点会对隧道结构长期性态的认识产生偏差。

Influence of long-term partial drainage of shield tunnel on tunnel deformation and surface settlement

It is reported that the long-term seepage of shield tunnel often results in significant settlements of ground surface and tunnel. A calculation method which meets the stiffness requirements of shield tunnel is firstly proposed to simulate the partial drainage of tunnel. The distribution of pore water pressure of soils around the tunnel, ground surface and tunnel settlement as well as tunnel deformation are investigated by considering different joint leakages in the context of the same magnitude of water inflow at steady state. The results indicate that the pore water pressure distribution, the settlement and tunnel deformation change significantly with variation of location of joint leaking. The pore water pressure around the tunnel decreases obviously when the leaking joint close to the tunnel invert, which results in larger ground surface and tunnel settlement. The tunnel will not only squat with time due to joint leaking, but occur horizontal displacement induced by unbalance loads. The distribution of pore water pressure, ground surface and tunnel settlement and tunnel deformation are all significantly different from those obtained by equivalent uniform drainage analysis. Finally, it is shown that the calculation without considering the partial drainage can not properly model the long-term behavior of the shield tunnel.