HIGHWAY MAINTENANCE: ADOT takes high-tech approach to lift freeway

Underground foam injection saves time, avoids major traffic disruptions

May 25, 2016
Underground foam injection saves time, avoids major traffic disruptions

When a section of freeway settles a bit, taking a high-tech approach to the repair work allows the Arizona Department of Transportation (ADOT) to give the roadway a lift without digging up the pavement.

That’s now the case along the Loop 101 (Pima Freeway) in the Scottsdale area, where ADOT is injecting a foam that hardens as it expands to stabilize the soil and lift the pavement. Crews have removed a minor roadway dip without the disruption of digging up and replacing part of the freeway.

The foam injections are being done as part of the ongoing ADOT project to widen and improve Loop 101 between Shea Boulevard and Loop 202 (Red Mountain Freeway). Repairing the depression in the freeway’s northbound lanes near McDonald Drive is one of the project team’s last work items before completing the addition of a new layer of smooth rubberized asphalt in that area.

Over time, ADOT and contractors have used the expansion foam at other freeway locations where the ground and pavement have settled. It has been used a number of times to lift concrete slabs on either end of freeway bridges. As the foam is injected beneath the freeway, it hardens as it expands and lifts the pavement while stabilizing the soil to guard against future settlement.

Before the foam injection is scheduled, ADOT geotechnical staff members have the job of examining the area where the ground beneath the freeway has settled to determine if the use of the foam is the recommended course of action. More advanced soil testing is then done using equipment to map the ground where settling has occurred. That helps give crews the information they need to inject the foam and stabilize the soil.