基坑开挖卸荷-加载对下覆盾构隧道影响研究

Study on the Effect of the Unloading and Loading in the Deep Excavation on Underlying Shielded Tunnel

为研究基坑开挖卸荷-加载过程对下覆盾构隧道的影响,以北京某近地铁建设项目为例,利用MIDAS GTS NX建立了地层-盾构隧道-基坑三维数值分析模型,并对其工程地质特征、岩土参数、基坑支护方式等进行了数值模拟试验。根据模型的计算结果,分析了在基坑开挖卸荷-加载施工过程中,基坑底部距隧道中心线距离与隧道直径的比值k对盾构隧道位移和应力的分布规律。计算结果表明:基坑开挖卸荷-加载施工对下覆盾构隧道的应力影响很小,对下覆盾构隧道顶部的变形影响较大,改变基坑底部到下覆盾构隧道水平轴线的距离,可以有效地减缓施工过程盾构隧道地变形,且当k值在4.0~4.5范围内基坑施工对隧道位移几乎没有影响。

To study the influence of the unloading loading process of the deep excavation on the underlying shielded tunnel,the Midas GTS NX is used to establish a three-dimensional numerical analysis model of the shielded tunnel and the deep excavation in a subway construction project near Beijing.The numerical simulation is performed based on the specific engineering geological characteristics,geotechnical parameters,excavation support type etc.The analytical results indicate that,the distribution patterns of the displacement and stress of the shielded tunnel by the ratio k of the distance from the bottom of the excavation to the centerline of the tunnel and the diameter of the tunnel during the unloading-loading construction process of the excavation are analyzed.The results show that:the excavation unloading loading construction has little effect on the stress of the underlying shielded tunnel,but it has great effect on the deformation of the top of the underlying shielded tunnel and changing the distance between the bottom of the excavation.The horizontal axis of the underlying shielded tunnel can effectively slow down the deformation of the shielded tunnel during the construction.The k is in the range of 4.0-4.5 has little effect on the displacement of the tunnel.