As a leading entertainment venue, this 735,000 sf, six-story arena is the regional epicenter for athletic events, concerts, and family shows in Western Pennsylvania. Hosting more than 150 events per year, PPG Paints Arena’s state-of-the-art design attracts national collegiate tournaments and is home to the Pittsburgh Penguins.
Fitting this structure in the middle of an urban setting on a sloping site presented challenges. The soils under the arena were highly variable. Subsurface conditions varied dramatically from shallow bedrock at one end of the arena to 35 ft of variable urban fill overlying soft alluvial deposits from an old stream bed. The highly variable fill consisted predominantly of very loose to dense rock fragments with concrete, brick, slag, coal, glass, wood, and sand, but also contained areas and pockets of very soft to stiff sandy and silty clay. Tight differential settlement criteria were established for the ice surface, event floor slabs and stadium footings. High groundwater and caving debris fill soils added to the site challenges.
The differential settlement criteria for the ice floor was 0.25 inch, and 0.5 inch for the other arena areas. To provide uniform settlement control, drilled shafts were used for arena footings, and Geopier elements were used for the ice floor and arena slabs. Given the variability of the underlying soils and the differing settlement criteria between the arena and ice floor, Geopier® elements were installed using both the Geopier and Impact Pier® installation methods. GeoConstructors, Inc. installed over 700 Geopier and 400 Impact pier elements on this project. Geopier elements were utilized for support of the ice surface since fill depths ranged up to 18 ft and were above the water table. As the fills got deeper, alluvial sands, groundwater and caving soils were encountered, Impact pier elements were installed up to 40 ft deep.
Proposed Limits for Geopier Support
Actual Geopier Layout