I17 Anthem: MSE Abutment Repair

The Arizona Department of Transportation (ADOT) retained NCSG to provide the geotechnical recommendations for the emergency repair of an MSE wall at an overpass of Interstate 17 (I17) near Anthem just north of Phoenix.

The driver of a fully-loaded 18-wheel semi-truck going south on I17 towards Phoenix lost control over his vehicle and crashed into the abutment wall of the Anthem Way overpass. The abutment includes a MSE structure with precast concrete panel facing. Concrete panels in the immediate vicinity of the crash were crushed and the steel strip reinforcement was bent, leaving a large hole in the wall. In the days following the crash, part of the reinforced soil mass flowed out of the hole due to the missing front panels, increasing the size of the hole even more.

ADOT approached NCSG to design a fix for the problem since the constantly worsening condition of the site threatened to affect the safety of the bridge.

NCSG designed a soil nail fix with shotcrete facing to ensure the structural soundness of the bridge abutment and hence the entire overpass. The design involved backcalculating the load on the MSE reinforcements and then transforming this load into an equivalent design load for the soil nails in order to obtain compatibility between the two different systems. A cast-in-place facing was hand carved to resemble the MSE wall panels and create a consistent look with the rest of the abutment. After a fresh coat of paint, you would be hard pressed to know anything ever happened there!

This project has been constructed and is currently in service.