历史建筑地下空间拓展工程

北京某历史建筑,在不改变建筑外观与紧邻景观条件下,采用新建内嵌式地下结构方案,实现既有地下室大跨度结构改造、增加层高与外部拓展。为进行大跨度结构改造,采用托换结构与新建地下结构合二为一的永久性托换结构,实现既有建筑内部承重结构的整体托换,避免了采用临时性托换在其拆除时引起的既有结构二次变形。为增加地下室层高,将永久性托换结构荷载及其承担的结构荷载向两侧传递到地基基础侧向托换结构的托换桩上,拆除既有地下室内部承重构件后,顺序进行土体开挖、地基基础侧向托换结构水平构件施工、永久托换结构下部新建地下结构施工。地基基础侧向托换结构在保持既有地基应力和变形状态、控制土体开挖引起既有建筑沉降的同时,对永久托换结构荷载起到中间传递功能。本文从地下空间拓展建筑与结构方案、荷载托换与传递体系、托换结构设计、结构稳定性、沉降控制、沉降监测等方面对工程情况进行了介绍。本工程采用的新建内嵌式地下结构方案及荷载托换技术具有普遍应用价值,可广泛应用于既有建筑地下空间拓展工程。

Underground Space Expansion Project of a Historical Building

Under the condition of not changing the appearance and adjacent landscape, a new built-in underground structure scheme is adopted in a historic conservation building in Beijing to realize the reconstruction of the long-span structure of the existing basement, increase the height of the basement and external expansion. In order to carry out the reconstruction of large-span structure, the permanent underpinning structure, which combines underpinning structure with newly-built underground structure is adopted to realize the integral underpinning of the internal load-bearing structure of the existing building, and the secondary deformation of the existing structure caused by the temporary underpinning structure and its removal is avoided. In order to increase the height of the basement, the load of the permanent underpinning structure and the load of the existing structure are transferred to the underpinning piles of the lateral underpinning structure of the foundation on both sides. The excavation of soil, the construction of lateral underpinning structure of foundation, and the construction of new underground structure under permanent underpinning are carried out sequentially. While retaining the stress and deformation of the existing foundation and controlling the settlement of the existing building caused by soil excavation, the lateral underpinning structure of the foundation plays an intermediate transfer function for the load of the permanent underpinning structure. This paper introduces the project implementation from the aspects of new built-in underground architectural and structure scheme, load underpinning and transfer system, underpinning structure design, structural stability, settlement control, settlement monitoring and so on. The new built-in underground structure and load underpinning technology adopted in this project is of universal application value and can be widely used in the underground space expansion project of existing buildings.