Sofi Stadium
One of the tallest mechanically stabilized earth walls in the world is obscured from view, hidden by the biggest sta- dium in the National Football League. At SoFi Stadium in Inglewood, California, RECo’s 100-ft tall Reinforced Earth wall was installed as a stress relief wall around the stadium footprint, forming a “bowl” for the main structure to be set below the original grade. About the Project If built on existing grade, the stadium would have invaded the nearby navigational airspace of the Los Angeles Inter- national Airport. To keep the final stadium elevation below the limitation, it had to be set approximately 100 feet into the existing grade. To move the project along as fast as possible and to begin stadium foundations at the earliest date possible, the contractor decided the best option was to excavate the 100-ft deep hole, then build a wall up concur- rently with the stadium structure inside the bowl. Why Reinforced Earth? Due to high seismic considerations in the Los Angeles area, it was necessary to design a bowl wall that would al- leviate potential dynamic forces from the stadium structure. Reinforced Earth MSE walls are highly flexible and can be designed to accommodate the most extreme seismic criteria. RECo’s engineering team was able to provide the contractor with a design that worked, and gained approval from the reviewers quickly. Reinforced Earth’s designs fast-tracked the construction schedule immensely. Overall, the wall was topped out in about a year and a half. The constructability of the wall system allowed the contractor to maximize their schedule and gave them the flexibility to build out of sequence and accommodate other design changes quickly. The MSE wall design saved the contractor millions of dollars and about a year of construction time. Materials The majority of the wall was built using concrete facing panels. Wire mesh facing TerraTrel™ panels were used in areas for temporary ramps down to the bottom of excavation, and to support fill behind other stadium features within the reinforced soil volume. Ribbed steel strips were used for soil reinforcement for the entire Reinforced Earth wall. Up to 13 soil reinforcements were connected to one 5-ft x 5-ft concrete facing panel.
Over 300,000 square feet of concrete and wire mesh facing panels were installed, the equiva- lent of more than five football fields. Over 1,500 miles of reinforcing strips were installed – the same distance the L.A. Rams traveled when they moved from St. Louis to Los Angeles. Other Challenges A variety of foundations for the stadium structure were located behind the wall facing inside the MSE wall reinforced earth volume. Within its fill, the wall had to withstand loads for the roof, stairs, upper level structures, and more. Hundreds of foundations (piles, shafts, footings) were located within the backfill, the largest of which were for the roof. They were accommodated by skewing reinforcing strips, placing additional reinforcing strips, and add- ing wire faced relief walls adjacent to the ob- structions to alleviate earth pressure on them.
The Reinforced Earth wall (left) is shown partially completed with stadium construction underway.
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csengineermag.com
FEBRUARY 2021
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