Observed Performance of a Large-Scale Double Annular Arched Girders Structural System in Deep Excavation

Abstract

Large amount of field and experimental data has been devoted to excavations supported by single annular arched girders structural system thus far. In contrast, only few data were available for excavations supported by double annular arched girders structural system, especially those with large diameters in thick soft clay deposits. Therefore, it is worthwhile to study such kind of cases. This paper investigates an excavation located in Pudong New Area, Shanghai. In this project, two reinforced concrete supports are arranged vertically, and the excavation can be divided into three areas. Area A is supported by double cylindrical arched girders structural system, the diameter of each arched girders is 86 m. Area C is supported by side girders and angle diagonal brace. Area B just uses angle brace to support it. This project is constructed by bottom-up method. Based on site measured data, this paper investigated items included: groundwater level changes, lateral wall settlements, subsurface horizontal movements, metro pier settlements, and annular concrete support force changes. As the result, we find that the double cylindrical excavation behaves much differently with single cylindrical excavation. This study provided valuable data and result for double cylindrical excavation design and construction. And we found the internal force distribution of the double annular support structure is complicated and is sensitive to the boundary conditions and the construction progress. In addition, casting of the base slabs is particularly important for the safety of the double annular support structure.