邻近隧道及周围地层受深基坑开挖影响的现场监测研究

In-situ Monitoring Analyses of the Influences of Deep Foundation Pit Excavation on Adjacent Metro Tunnels and Surrounding Strata

  • 摘要: 深大基坑施工诱发的运营隧道变形以及周围土体沉降等施工问题, 在我国城市轨道交通施工安全控制和风险评估中受到日益关注。文章基于上海市交响乐团在建基坑工程, 结合运营隧道以及基坑围护结构监测数据, 分析了基坑不同开挖阶段周边地表沉降、 地下连续墙变形、 运营隧道收敛变形以及竖向位移的规律和特点。实测结果表明: 周边地表总体呈下沉趋势, 大致呈抛物线型分布;坑外土体侧斜和围护墙体侧移具有基本相同的变化规律, 且均向基坑内侧移, 开挖深度对土体侧移的影响并不是简单的线性关系;隧道的水平附加收敛表现为向外拉伸, 随基坑开挖的进行, 收敛变形增幅明显;隧道净沉降曲线与基坑周围土层、 围护结构变形曲线的变化趋势具有较好的一致性;地下连续墙两侧 SMW工法加固可有效控制隧道、 坑外地表以及地下连续墙的变形。研究成果可为正确制定软土城区基坑施工对邻近地铁隧道的保护措施提供一定的理论依据。

     

    Abstract: The operating tunnel deformation and soil mass settlement induced by deep foundation pit excavation are highly concerning in urban rail transit construction safety management and risk assessment. Based on the Shanghai Symphony Orchestra foundation pit project and the monitoring data for the operating tunnel and enclosure structures, the rules and characteristics of surrounding ground settlements, diaphragm wall deformations, horizontal convergence and vertical displacements of the foundation pit at different construction stages are analyzed. The measured results show that the overall trend of ground settlements is one of sinking and is generally presented in a parabolic distribution; the lateral deformations of the soil mass and diaphragm walls present substantially the same variation, which moves towards the inside of the foundation pit, and the influence of excavation depth on the horizontal displacements is not a simple linear relationship; horizontal additional convergence is presented by stretching outward, and the convergence increases with the excavation of the foundation pit; and the SMW reinforcement for both sides of the diaphragm wall can effectively control the deformation of the tunnel, the surface outside of the foundation pit and the diaphragm walls.

     

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