Excavation of Middle Huai-Hai Road Station of Shanghai Metro Line 13: Challenges, Risks, Countermeasures, and Performance Assessment

This paper reports on the construction of a 31.4- to 33.1-m-deep subway station in Shanghai, China. This underground transit project was complicated further by the in situ hydrogeological condition, congested construction environment, and additional side-by-side deep excavations for other underground facilities. To protect the urban environment, challenges of this project, including potential risks, were evaluated in advance, and corresponding countermeasures to cope with potential risks were considered in the design and construction. To achieve the best project performance and verify design and construction considerations, a long-term field instrumentation program that lasted from May 2012 to April 2016 was implemented to monitor performance of the subway station pit and the adjacent ground and superstructures. Field data revealed that displacements of earth-retaining structures and the ground were within the local deformation control criteria. With the exception of a local leaking accident, no through-wall-seepage flow, piping, sand boiling, soil flow, rupture of pit base, or hydraulic uplifting of basal soils took place during the construction. The monitored cumulative settlements of adjacent buildings exceeded the specified criterion, but most buildings underwent only rigid tilt settlements and were rarely damaged. Experiences and lessons learned from this project will be useful for future design and construction of deeply buried infrastructures in densely populated cities.