软土基坑卸荷对下卧既有隧道纵向变形影响研究综述

Overview on the Influence and Control Measures of Vibration Induced by Shield Construction on Adjacent Buildings

为全面了解软土基坑开挖对既有隧道纵向变形的影响,掌握既有隧道在基坑近接施工下的纵向变形响应特征以减少开挖对邻近既有隧道的影响。文章从理论研究、数值模拟以及实测分析等3个方面对国内外相关研究进行了总结,同时提出了基坑开挖对下卧隧道最大位移影响范围的实用边界模型,之后给出了有待下一阶段进一步研究的方向。主要结论如下:现有的分析方法都依赖于隧道处于假设状态的初始条件,未考虑隧道的已有“损伤”;数值模拟结果的合理性很大程度上依赖于所选择的本构模型与参数取值,更加适用于复杂应力条件的本构模型将是未来研究的重点;卸荷比对下卧既有隧道的影响明显,在软土地区的隧道上方进行基坑开挖,可通过调整卸荷比来减小对下卧隧道的扰动。随着基坑卸荷比的研究从“一维”逐步深入到“三维”,基于卸荷比的基坑开挖对隧道位移影响的预测准确度更高。

To fully understand the influence of soft clay foundation pit excavation on the longitudinal deformation of the existing tunnel,this paper summarizes the relevant research all over the world from three aspects:theoretical research,numerical simulation and measured analysis,in order to reduce the harm of excavation to the existing tunnel and master the longitudinal deformation response characteristic under the compact construction of foundation pit.A practical boundary model of the influence range of excavation on the maximum displacement of the underlying tunnel is proposed.Then the direction of further research in the next stage is suggested.The main conclusions are as follows.The existing analysis methods rely on the initial conditions of the tunnel in the assumed state,and ignore the existing“damage”of the tunnel.The rationality of numerical simulation results largely depends on the selected constitutive model and parameter values,therefore the constitutive model more suitable for complex stress conditions will be the focus of future research.The unloading ratio has an obvious impact on the underlying existing tunnel.The disturbance to the underlying tunnel can be reduced by adjusting the unloading ratio.With the research of foundation pit unloading ratio from“one-dimensional”to“three-dimensional”,the displacement prediction accuracy of the influence of foundation pit excavation on tunnel displacement based on unloading ratio is higher.