A Study of Deep Foundation Solutions for a Challenging Transit Oriented Project

This case history summarizes the foundation design of an 11-story hotel that was constructed above and around an existing transit headhouse structure in the South Boston Seaport District. The hotel was designed to span over the headhouse structure at the third-floor level and be supported on a line of exterior columns at the eastern end of the building. This paper discusses how unique site and design challenges were considered and solved for the foundation design and construction. These challenges included protecting existing and adjacent structures, overcoming buried obstructions, and supporting high vertical and shear loads. Multiple foundation systems were evaluated. Deep, driven steel H-piles were ultimately selected to support new building column loads; however, along the eastern side of the headhouse, significant shear loads were imposed on the foundations. To resist these loads, the authors designed a “composite” foundation element consisting of end-bearing H-piles encased within a circular concrete section.