含沼气地层中气体运移对隧道结构的影响分析

Effect of Gas Migration on a Tunnel Cross a Gassy Stratum

沿海或沿江隧道可能要穿越富含有害气体的地层,给隧道施工安全带来挑战。依托上海市天然气主干管网崇明岛-长兴岛-浦东新区五号沟LNG站管道工程的过江隧道,建立了非饱和土固液气耦合数值分析模型,模拟隧道周围气藏的气体汇聚和逸散过程,重点分析气体运移过程对土体变形和隧道结构受力性状的影响。研究表明,气体汇聚过程将导致隧道周围土体抬升,气体逸散过程则导致土体沉降,气体迁移导致隧道衬砌结构的内力也随之变化,经分析确认衬砌结构的弯矩和轴力均未超过设计值,衬砌结构安全。

Coastal or riverside tunnels may go through gassy strata,which pose risk to construction of the tunnels.This study established a solid-liquid-gas coupled numerical model of unsaturated soil for simulating the gas pressure build-up and dissipation around the river-crossing tunnel of No.5 Trench LNG Station Pipeline Project in the Shanghai’s main Natural Gas Pipeline Network involving Chongming Island-Changxing Island-Pudong New Area,a numerical analysis model of unsaturated soil solid-liquid-gas coupling is established to simulate the gas convergence and dispersion process of the gas reservoir around the tunnel,focusing on the influence of the gas transport process on the deformation of the soil and the tunnel structure.The numerical results show that the surrounding soil rise as gas gathers,and settle as gas escapes,the internal forces in the liners of the tunnel change accordingly,however,the moments and the axial forces received by the liners are less than the allowable values and therefore the liners remain safe despite of gas migration.