Foundation Systems of Boston's Big Buildings
Boston lies at the head of an island studded harbor. Millions of years filled with volcanic events and glacial ice movement formed the bedrock and much of the subsurface conditions of the city. The ice eroded the bedrock under Boston, and did not erode harder rock to the north and south, creating a prolific harbor. Cambridge argillite, a slightly metamorphosed, layered, and sedimentary rock, is the softest and most abundant of the Boston. It has an allowable bearing pressure of 78,000-195,000 kg/m^2, making it a good material to bear large buildings on, hence Boston’s abundant skyline. Also present in the south and west of Boston is Roxbury Conglomerate, a sedimentary stone with an allowable bearing pressure of 195,000-975,000 kg/m^2.
Although Boston’s bedrock is strong, engineers face some obstacles in foundation design. Soft-Rock Alteration, which occurs when deep weathering or hydrothermal alterations trigger kaolinization, causes the hard rock to turn plastic and claylike. Additionally, the bedrock is very shallow in some areas. Like many older urban centers, much of Boston’s land is reclaimed; about a sixth of the usable land in Boston today has been filled in. Because of the fill, the quality of soil varies in both thickness and quality from place to place.
Boston’s dynamic subsurface profile, in addition to its industrial prominence, have led to the rise of tall buildings with creative foundation strategies. This website will explore said strategies employed by some of Boston's infamous and large structures.
Although Boston’s bedrock is strong, engineers face some obstacles in foundation design. Soft-Rock Alteration, which occurs when deep weathering or hydrothermal alterations trigger kaolinization, causes the hard rock to turn plastic and claylike. Additionally, the bedrock is very shallow in some areas. Like many older urban centers, much of Boston’s land is reclaimed; about a sixth of the usable land in Boston today has been filled in. Because of the fill, the quality of soil varies in both thickness and quality from place to place.
Boston’s dynamic subsurface profile, in addition to its industrial prominence, have led to the rise of tall buildings with creative foundation strategies. This website will explore said strategies employed by some of Boston's infamous and large structures.