近接下卧既有盾构地铁线路基坑开挖方法研究

Study on Excavation Method of Foundation Pit of Adjacent and Underlying Existing Shield Metro Line

在城市轨道交通既有线隧道上方近距离进行基坑开挖,对既有线的变形控制要求高,施工方案和措施必须得当。针对深圳市岗厦北枢纽工程南区基坑开挖工程,采用三维动态施工数值模拟分析方法,分析了不同开挖方案对下方近接既有地铁10号线盾构区间隧道结构位移和内力的影响,并结合洞内变形、结构承载力、轨面差异沉降等指标,依据规范对不同开挖方案下既有线隧道的安全性进行了评价,最终基于研究分析结果,建议选取短分块、小坡率的开挖方法进行近接下卧既有盾构地铁线路的基坑开挖施工。

The excavation of foundation pit near the existing line tunnel of urban rail transit requires high deformation control of the existing line,and the construction scheme and measures must be appropriate.In view of the foundation pit excavation project in the south area of Gangxia North Junction Project in Shenzhen,the three-dimensional dynamic construction numerical simulation analysis method is adopted to analyze the influence of different excavation schemes on the structural displacement and internal force of the shield tunnel adjacent to the existing Metro Line 10 below,and the safety of the existing line tunnel with different excavation schemes is evaluated according to the specifications in combination with the indexes such as the deformation inside the tunnel,the structural bearing capacity,and the differential settlement of the rail surface.Based on the research and analysis results,it is suggested that the excavation method of short block length and small slope ratio be selected for the excavation of foundation pit close to the existing underground shield metro line.