Covered Semi-Top-Down Excavation of Subway Station Surrounded by Closely Spaced Buildings in Downtown Shanghai: Building Response

Abstract

AbstractBased on field data, this study investigates responses of six pre-existing buildings to an adjacent 24.8–25.2 m deep subway station excavated by the covered semi-top-down method. During excavation of 1 m wide and 50.2–50.5 m deep slurry trenches for diaphragm wall panels (i.e., diaphragm walling), buildings on both shallow and deep foundations developed noticeable settlements up to 15 mm. Subsequent excavation of the upper 15.9–17.7 m thick soils inside the pit only incurred limited building settlements less than 10 mm, which contrasted sharply with remarkable displacements of the diaphragm wall and ground nearby. As excavation continued to the final level, buildings on strip footing, stiffened raft foundation, strip footing atop long piles, and short piled raft foundation settled dramatically up to 40 mm, but those on long piled raft foundation still were hardly displaced. Like diaphragm wall and ground, all buildings developed significant postexcavation settlements up to 34.5 mm. Eventually, int...