Geotechnical Design of Retractable Roof Arch Foundations

Geotechnical Design of Retractable Roof Arch Foundations—Cowboys Stadium

Gregory, Garry H.

One of the challenging engineering aspects of the new Cowboys Stadium in Arlington, Texas was design of foundations for the retractable roof arches. The two arches, with a clear span of approximately 393 m (1,290 ft), produce a lateral thrust of approximately 86,740 kN (19,500 kips) at each foundation with the lateral thrust line 32 degrees from horizontal. Design criteria included a maximum allowable deflection of approximately 12 mm (0.5 inches) for the foundations. Adding to the complexity was the varying geologic conditions with dense sand being predominant at one end of the arches and sandy shale being predominant at the other. Initial options considered by the design and construction teams included large mat foundations oriented perpendicular to the line of thrust of the arches, horizontal mat foundations with tie-down anchors, both vertical and battered drilled shaft groups, and battered micropile groups with both tension and compression elements. These options were determined to be problematic due to excessive deflection and/or constructability issues. Subsequently, the geotechnical design team proposed a foundation system consisting of slurry-placed diaphragm walls. This option resulted in a foundation system that is completely in compression without tension elements and provided a much stiffer system that could meet the deflection criteria. Preliminary dimensions of the diaphragm wall foundations were established based upon soil strength data obtained from field and laboratory testing. Final dimensions were confirmed based on instrumented load testing of two full-depth sacrificial diaphragm wall panels installed and tested prior to final design.