Abstract:
The proposed “ Fenway Center” project will create more than 1, 000, 000 SF of finished building space within two new high-rise buildings in the heart of Boston. Unlike most construction projects built on land, this development is currently taking place over the Massachusetts Turnpike, an active eight-lane highway traveled by more than 100, 000 vehicles each day.
In order to accommodate all of the loads imposed by the new buildings, a concrete deck must be constructed over a 750 feet segment of the entire highway. This deck will rest atop three heavily-reinforced and parallel concrete walls, supported by more than 800 high-capacity piles. For most of the center (median) and northern (westbound) walls, driven piles are being utilized to support the high loads. In more congested areas of the site including the entire southern (eastbound) wall located between the Mass Pike and an adjacent railroad corridor, drilled micropiles (“ DMPs” ) were the most practical deep foundation option.
In addition to a major interstate running through its center, the project site is surrounded by several buildings to the north, two heavily-traveled railroad tracks to the south, and busy public roadways (Beacon Street and Brookline Avenue) to the west and east, respectively. These site constraints have posed a number of construction challenges, including limited work zone access for equipment and personnel, minimal on-site storage for materials, and vibration concerns to name a few. To make matters worse, the site’ s geology included some of the thickest overburden deposits to be found within the city limits, and none were capable of providing adequate bearing for the heavily-loaded deep foundations. Instead, every pile on the project would need to derive its capacity from the underlying competent bedrock formation located 170 to 250 feet below existing ground surface.