Below Boston's New Bridge

The Charles River Bridge, a 10-lane cable-stayed structure will be the widest cable-stayed bridge in the world. The bridge is 1,460 ft long with a main span between towers of 745 ft. This unusual cable-stayed bridge offered many technical challenges to the designers. The bridge was designed to avoid conflicts with an existing bridge that needs to remain in use until the new bridge is open to traffic. The site has complex bedrock conditions and the potential for liquefaction-induced ground instability. Also, the bridge tower foundations are located near an active subway tunnel. As a result, 8-ft-diameter drilled shafts, socketed into the underlying bedrock, were selected for the design. Permanent isolation casings installed around the shafts nearest the subway tunnel allow the shafts to deflect within the casing without imparting load to the tunnel.