Observed Performance of a Large-Scale Deep Triangular Excavation in Shanghai Soft Clays

An 18.4-m-deep triangular foundation pit with in-plane excavation area of approximately 10,000 m 2 was constructed in soft clay. The excavation located at Hongqiao comprehensive transportation hub center in Shanghai, in which an energy gallery, many underground pipelines, and viaduct piers exist. Deformation characteristics of the foundation pit and the impact on the adjacent buildings and structures were observed by a monitoring system during excavation. Field data including wall deflections, vertical wall movements, ground subsidence, as well as vertical column movements were analyzed and compared with other excavations of metro stations or rectangular excavations in Shanghai. This excavation exhibited different deformation characteristics from other excavations because of its triangular shape with acute corners. The deformation law of this special excavation was beneficial for the design and construction of special-shaped foundation pit in complex environment.