To provide a controlled environment and avoid using any of the restricted campus land available, the design team created an underground library by building the facility within an excavated sandstone cavern beneath the campus of the University of Minnesota in Minneapolis, Minnesota. The $41.5 million project consists of two storage caverns, a four-story conventional surface building, two vertical shafts and a mined portal entry. The cavern walls were lined with curved precast concrete wall panels that were back-grouted to provide complete structural support. Erecting these panels required the development of unique handling equipment that set the panels with tight tolerances. The building constructed within this restricted space features Ioadbearing precast concrete walls supporting a solid-slab precast roof attached to bolts in the cavern’s roof at its center gable. This article presents the enormous challenges posed in underground construction and discusses the role that precast concrete played in solving these problems despite the restricted space.
