软土地区深大基坑紧邻高铁隧道施工影响研究

Research on Construction Influence of Deep Foundation Pit Adjacent to High-speed Railway Tunnel in Soft Soil Area

软土地区深大基坑施工难度大、安全风险高,紧邻既有高铁隧道基坑施工易引起隧道结构变形、开裂、渗漏水等病害,故有必要采取有效安全保护措施确保高铁运营安全。以天津某基坑工程紧邻高铁隧道施工为研究背景,运用有限元分析手段,结合现场实测结果,研究高铁隧道结构变形规律及安全保护措施。研究表明,该基坑施工引起既有高铁隧道结构产生最大水平位移为4.14 mm,最大竖向位移为0.92 mm,结构变形以水平方向为主;基坑内结构承载桩采用静压预制桩时,挤土效应明显,调整为钻孔灌注桩后,隧道结构水平位移由4.14 mm减小至3.12 mm;采取安全保护措施能够有效减小基坑施工对既有结构的扰动,基坑施工完成后,隧道结构位移小于1 mm。

The design and construction of deep and large foundation pit in soft soil area is difficult with high safety risks. The foundation pit construction adjacent to the existing high-speed railway tunnel will cause deformation, cracking, leakage and other diseases of the tunnel structure. It is necessary to take effective safety protection measures to ensure the safety of high-speed railway operation. Based on the construction of a high-speed railway tunnel adjacent to a foundation pit project in Tianjin, this paper studies the deformation law and safety protection measures of the existing high-speed railway tunnel structure by means of finite element analysis and field measurement results. The results show that the deep foundation pit construction in soft soil area causes the maximum horizontal displacement of 4.14 mm and the maximum vertical displacement of 0.92 mm, and the structural deformation is mainly along the horizontal direction. The soil squeezing effect is obvious when the static pressure precast pile is used in the bearing pile of the foundation pit. The horizontal displacement of the tunnel structure does not continue to increase after adjusting to the bored pile, and the horizontal displacement is reduced from 4.14 mm to 3.12 mm. Taking safety protection measures can effectively reduce the disturbance of existing structure caused by foundation pit construction, and the displacement of tunnel structure is less than 1 mm after foundation pit construction.