ABSTRACT
This construction project involved renovating Minami-sunamachi station on the Tokyo Metro Tozai Line by converting it from a single island platform station with one set of tracks on each side into a two-platform station with three sets of tracks. Minami-sunamachi Station was constructed using the caisson method in what was a canal at the time of construction; even now, the ground surrounding the box elements is very soft. Thus, measures to minimize displacement of the surrounding ground and existing box elements were required for each process of renovating the station. As for the construction work, excavation was performed to a depth of 14 m using the cut-and-cover method. For earth retention, diaphragm walls were used in an effort to make use of existing structures. For reinforcement, ground struts were installed below the base of the excavation area and performed ground improvement to improve the base.
