Custom Injection Pattern Solves Settlement Issue in Tennessee

The Challenge

Settlement Issues Threaten Road Closure

Outside Tullahoma, Tennessee, the approaches on both sides of a triple box culvert had settled repeatedly over the years, resulting in dips at the surface and poor rideability. The asphalt paving was overlaid multiple times, and state highway officials had tried other more extensive repairs as well. Despite all their efforts, the settlement issues continued to persist and worsen. At a point when road closure was being debated, TDOT reached out to Groundworks.

Key Facts

The Solution

16 ft voids filled with Polyurethane Injections

Upon inspection, Groundworks crews determined that the back-fill materials against the side of the box culvert were consolidating and subsiding. Most often when this happens, it is due to poor compaction of unsuitable materials used in the back-fill. The road above is four lanes wide with an additional center lane and full shoulders, adding to a width of over 90 feet. To inspectors on the scene, the settlement issue appeared to extend the full width of the road at both ends of the culvert. Groundworks proposed its Polyurethane Injections process to stabilize the soils at both ends of the culvert and lift the roadway back to its proper grade.

Groundworks developed a job-specific injection pattern to stabilize the back-fill and lift the pavement, thus smoothing out the dips and restoring safety and comfort to drivers. The injections were designed to a depth of 16 feet next to the box culvert, equal to the depth of the box culvert from the road surface. This full-depth treatment would minimize the chance of future settlement much more effectively than a shallow treatment alone could.

The Impact

Culverts and roadway structures stabilized in 6 days.

Over six working days, and with minimal impact to traffic, Groundworks injected polyurethane grout into the back-fill soils on both sides of the culvert. The injection successfully lifted and leveled the dips to improve rideability and stabilized the deeper supporting soils to mitigate future settlement. After so many years of fighting this persistent problem, TDOT officials were extremely happy with the results.