- Conference Article
- 10.1061/9780784485842.013
Supporting the Illinois State Capitol
- Nov 14, 2024
- Stanley L Worst + 2 more +2
Constructed almost 150 years ago, the Illinois State Capital building is both a historic and sensitive structure. In 2022, the State of Illinois announced that the north wing of the existing Capital Building would be renovated, including lowering portions of the existing basement and construction of an adjacent underground conference center with associated connecting tunnels. Construction of the new basement involved a 30-ft-deep excavation adjacent to the existing structure. This required lowering of the foundations on both the interior and exterior of the existing building using underpinning. Lateral support for the underpinning, where required, was provided by permanent tiebacks. The non-building sides of the excavation were supported with a conventional excavation support system consisting of drilled-in soldier piles, wood lagging, and tiebacks. The excavation support system was designed for both the temporary excavation condition to allow construction of the underground conference center and the permanent condition to support the long-term lateral earth loads for the conference center walls.
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