含气地层不均匀沉降对盾构隧道结构影响的固-液-气耦合分析

Solid-Liquid-Gas Coupled Analysis of the Influence of Uneven Settlement in Gassy Soil Layer on the Structure of a Shield Tunnel

为掌握含气地层中盾构隧道渗漏气引起的地层变形对隧道结构的影响,以苏通气体绝缘金属封闭输电线路(gas-insulated metal enclosed transmission line,GIL)项目中江底富含高压浅层气地层为研究对象,利用自主开发的有限元程序,并采用非饱和弹塑性本构模型,对含气地层不均匀沉降对盾构隧道结构的影响进行了三维固-液-气耦合数值模拟分析。结果表明:排气引起的地层不均匀沉降会导致隧道沉降,产生附加内力。其中,渗气口附近沉降位移最大,含气地层下部由于卸荷效应会有少许回弹;同时,沉降位移最大处所在截面的附加弯矩也最大;越远离含气层的位置,截面附加弯矩越小。

To understand the influence of soil deformation on shield tunnel structure due to the leakage of gas in gassy soil layer,the soil layer at the bottom of Yangtze River in Sutong gas-insulated metal enclosed transmission line(GIL)project,which contains large amounts of high-pressure shallow gas,was taken as the research object,and a numerical simulation of the influence of uneven settlement in gassy soil layer on the structure of a shield tunnel was carried out.A self-developed finite element program was used for the three-dimensional solid-liquid-gas coupled simulation,and an unsaturated elastoplastic constitutive model was adopted in the study.The results show that the uneven settlement of the soil layer caused by gas release may lead to the tunnel settlement and generate additional internal forces in the structure.The settlement near both sides of the gas permeation port is the largest,and the lower part of the gassy soil layer rebounds slightly due to the unloading effect.Besides,the largest additional bending moment occurs at the section where the settlement is the largest.The further away from the gassy soil layer,the smaller the additional bending moment will be.