合肥地铁盾构隧道下穿河道施工数值模拟分析

Numerical simulation analysis of Hefei metro shield tunnel crossing river

文章针对合肥地铁1号线盾构下穿南淝河存在的安全隐患,基于流固耦合原理与有限差分方法,采用FLAC3D对隧道盾构开挖流固耦合效应进行模拟,分析了盾构推进过程中隧道周边土体孔隙水压力规律、竖向应力场、拱顶沉降等。研究表明:盾构开挖导致隧道拱顶及两侧土体孔隙水压力明显降低,地下水在水压力的驱动下向拱顶与两侧流动,这些部位容易出现危险,要防止涌水事故的发生;考虑流固耦合后,围岩竖向应力值变大,最大拉应力与压应力均变大,隧道周边局部围岩出现较大的应力集中现象,对隧洞安全不利,拱顶竖向位移增大,竖向位移在水平方向从隧道中心向两侧不断减小,而土体后期固结沉降占最终沉降的比例达到30%,要加强后期监测,防止沉降过大影响隧道安全。

In order to resolve the potential danger of shield tunnel crossing Nanfeihe River on Hefei Metro Line 1, the fluid-structure interaction effect was simulated based on fluid-structure interaction principle and finite difference method by FLAC3D, and the pore water pressure around the tunnel, ver- tical stress field and crown sedimentation induced by shield structure excavation were analyzed. It was indicated that the pore water pressure around the arch apex and surrounding soil was seen great reduc- tion, so the underground water driven by the pressure difference tended to flow into these areas, which might present danger such as water burst. Considering the fluid-structure interaction principle, the vertical stress value of surrounding rock would grow; the maximum tension stress and pressure stress would also grow. A massive stress concentration occurred in surrounding rock of tunnel is dan- gerous. The vertical displacement of arch apex grew and this value constantly decreased from center to the sides horizontally. The proportion of later consolidation settlement in the ultimate settlement could reach 30%. So the further monitoring was needed to keep the tunnel from risks by massive set- tlement.