Steve Weyda, P.E., recalls a rigid inclusion hybrid solution that supports a new performing arts center in Eau Claire, Wis., situated at the confluence of two major rivers.
The Pablo Center at the Confluence is a state-of-the-art performing arts and education center resulting from public-private development for the Eau Claire community and the University of Wisconsin – Eau Claire. Located at the confluence of the Eau Claire and Chippewa Rivers, it is part of a larger project that includes retail and commercial space, student housing, a public plaza and pedestrian-bike paths along the river.
Our team at Ground Improvement Engineering was brought in early to the structural engineering design process following the geotechnical investigation. The investigation found sand fill over organics in some parts of the site, including layers of wood and sawdust from Eau Claire’s historic paper mill era. This soil profile can be problematic for heavily loaded structural conditions like the Pablo Center, which is designed with large open areas for public gatherings and performance spaces.
In addition, the confluence of two rivers creates the potential in the area for flooding. Our design solution considered the structural loads over organics as well as building features that fall below the groundwater table.
Our experience with soil profiles in Wisconsin led us to recommend one ground improvement solution for the non-organic areas of the site and another solution for the organics.
For the foundation work, we used the Geopier Armorpact system, a rigid inclusion ground improvement method that both reinforces and stiffens poor soils, and provides confinement of the aggregate pier. The unique Geopier® technology (Rammed Aggregate Pier®) provides a stable bearing layer for spread footing foundations; no special load transfer platform is required.
Under the slabs, we chose the Geopier Impactt® system, constructed to improve the loose sand and soft organic soils during installation.
In concert with our rigid inclusion pier installation across the site, we consulted on a solution to resist hydrostatic uplift in the event of groundwater rise. While our pier system supports the compressive loads of the structure, another contractor installed helical anchors to provide uplift resistance of footings that could be subjected to hydrostatic uplift during flood events.
To manage the tight construction timeline that also accounted for holiday breaks, our team installed more than 1,400 piers between late November and late February 2018. This was mainly during the often-harsh Wisconsin winter. The owner and general contractor trusted us to deliver in these conditions thanks to our past performance on challenging sites. We helped to keep the project on its timeline for a 2019 opening.
To learn more about how we work with Design Teams, visit our client page.
You may also be interested in this blog post about managing groundwater levels.