word of the week: CAISSON

The first of the Chicago Spire's Caissons

CAISSON: A watertight enclosure that extends from the base of a building to hardpan or rock below, inside of which construction work is carried out underwater or in marshy soil. Caissons are driven down to solid earth and then emptied of their contents, thus creating a dry space for working. Next concrete is poured into the empty tubes to create a foundation. Caissons can be critical in supporting heavy structures, especially in sludgy soil.

Look at the picture above of one of the Chicago Spire’s caissons running deep down through Chicago’s marshy soil. The Chicago Spire, designed by Santiago Calatrava, was intended to be the tallest building in the country. Due to the suffering economy, the building was never completed. Instead of being Chicago’s tallest building it’s our largest hole. Only the foundation was ever finished — supported by a number of caissons.

To the right see a picture of a caisson drilled into the earth prior to being filled with concrete.

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