One Financial Center
One Financial Center, completed in 1983, towers above the Rose Kennedy Greenway in the center of the Boston business district. With 46 stories and 2 levels below the surface, this building is one of the tallest in Boston at 590 ft. It sits on top of the Original Shawmut Peninsula, where Boston was initially founded. The Peninsula is primarily formed of glacial deposits with till over Cambridge Argillite bedrock. The soil is a glacial deposit composed of well stratified sands and gravels that range in thickness between depths of 3 and 7.5 meters. They are medium compact and are an important bearing stratum for supporting light to medium weight structures. However, the One Financial Center building is a large structure so a concrete mat was used to support the structure.
Concrete mats extend below the entire building and distribute the load from multiple columns and walls of the structure to the soil below. They may be used for an entire building or a portion of the building, and are sometimes used to resist water pressures when groundwater extends above the level of the floor of the lowest basement of a building. The selection of the type of foundation to be used for an individual structure is typically a function of the expected loads and the allowable bearing pressures. Typically, a mat foundation is only considered when the area of the spread footings or combined footings exceeds about 50 percent of the gross area of the building. Gaining Ground: A History of Landmaking in Boston-- by Nancy Seasholes
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