既有建筑下地下空间开发中竖向托换设计及其对上部结构的影响分析

上部结构的安全是实现既有建筑下地下空间开发的核心问题之一，以上海某历史建筑下地下空间开发为例，对上部结构进行竖向托换设计，并开展其对上部结构的影响分析。背景工程为地上4层砖木结构建筑，拟在建筑下方新建3层地下室，基础埋深约16m。基于施工净空条件的限制和托换构件入土深度的要求，采用低净空条件下的高承载力锚杆静压桩作为上部结构基础的竖向托换构件，着重对托换桩的分散布置、集中布置、分散结合集中布置三种方式进行了分析。并对地下空间开发过程中不同阶段上部结构受力及变形状态进行了有限元分析。结果表明：低净空条件下的高承载力锚杆静压桩可作为既有建筑竖向托换构件;竖向托换构件可采用“分散与集中相结合”的布置方式，有利于控制上部结构的变形和附加内力。

Vertical underpinning design of underground space development under existing buildings and its influence on superstructure

The safety of the superstructure is a core issue of underground space development (USD) to exist buildings. Taking the USD under a historical building in Shanghai as an example, the vertical underpinning of the superstructure was designed and its influence on superstructure was analyzed. The four-story wood and masonry building without basement is located in Shanghai. Under the building, it is planned to build a three-story basement with buried depth of about 16 m. Based on the limitations of construction clearance conditions and the requirements of the buried depth of the underpinning components, the pressed pile by anchor rod with high bearing capacity under low headroom conditions was proposed as the vertical foundation underpinning component of the superstructure. Three layout plans of underpinning piles such as scattered layout, centralized layout and combination of scattered and centralized layout were discussed. The finite element analysis results of the stress and deformation at various USD stages under the existing building were also carried out. The results show that the pressed pile by anchor rod with high bearing capacity under low headroom conditions can be applied as the vertical underpinning component under the existing buildings; the combination of scattered and centralized layout is beneficial to control the deformation and additional internal forces of the superstructure.