隧道基坑穿越建筑桩基保护方案探讨

Protection Scheme Study of Tunnel Foundation Pit Goes Through Building Pile Foundation

城市核心区隧道基坑施工不可避免地对邻近建筑桩基产生影响,特别是桩基位于基坑壁时,基坑施工风险和保护难度更大。渝中连接隧道穿越重庆核心区渝中半岛,其周边高楼林立,明挖段基坑壁紧靠桩基。依托此工程,从技术、经济、社会影响等方面,对桩基托换、地圈梁+扩大基础加固、异形钢板+预应力锚索的桩基加固保护等方案进行了综合分析比较,在传统桩基托换方案无法实施的情况下,提出采用异形钢板+预应力锚索的桩基加固保护方案。通过三维有限元数值模拟,分析了施工过程岩土体位移、桩基变形、桩基应力、钢板与锚索应力等发生和发展规律。结果表明,该保护方案可以有效控制桩基变形和应力,能够确保施工过程建筑物的安全。本项目方案可为类似工程设计施工提供有益借鉴。

The tunnel excavation in the core area of city inevitably has impact on adjacent pile foundation,especially when the pile foundation located next to foundation pit,thus the construction is risky and protection confront more difficulties. The Yu-zhong city tunnel in Chong-qing city passes through the core area of Yu-zhong peninsula and is surrounded by high-rise buildings,whose excavation section of foundation pit lies next to the pile foundation. Based on this project,technology,economy and social influence were considered,comprehensive analysis and comparison on the pile underpinning scheme,ring beams and expansion of the foundation reinforcement,special shaped steel and prestressed anchor cable pile reinforcement protection scheme were conducted. As the traditional underpinning scheme cannot be implemented,a special shaped steel and prestressed anchor cable pile reinforcement protection plan was put forward. The developments of soil displacement,deformation and stress of pile foundation,steel plate and anchor stress under construction were analyzed by three dimensional finite element numerical simulation. The results show that the proposed protection scheme can effectively control the deformation and stress of pile foundation and ensure their safety under construction. The project scheme can provide some useful references for similar engineering design and construction.