Custom Injection Pattern Solves Settlement Issue in Tennessee


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 URETEK.


Upon inspection, URETEK 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. URETEK proposed its URETEK Deep Injection® process to stabilize the soils at both ends of the culvert and lift the roadway back to its proper grade.


URETEK 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.


Over six working days, and with minimal impact to traffic, URETEK 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.

URETEK Deep Injection® (UDI)

Widely referenced throughout our industry, UDI involves the injection of structural polymer into base and subgrade soils to increase the load bearing capacity. This is achieved by injecting the polymer through small holes drilled directly through the pavement structure to depths determined by site-specific analysis. Our URETEK 486 Star® material flows easily into voids and weak zones within the soil mass below. Through a controlled chemical reaction, the expanding polymer compacts surrounding soils and applies a controlled pressure on targeted areas of the affected pavement above. If needed, a multi-injection design plan is utilized to gently return the pavement to its original grade. The composite material quickly cures into a strong, dimensionally stable, and water-resistant geo-material, providing years of reliable service.

URETEK 486 Star®

URETEK 486 Star® polymer is a two-component, high-density, expanding thermoset polyurethane system. It was developed to be the ideal solution for under-sealing, void filling, lifting of settled pavement, stabilization and stiffening of weak soils, and for encapsulating and sealing buried infrastructure. URETEK 486 Star® is environmentally inert, non-toxic, and resists underground water erosion or weakening due to its industry-leading hydrophobic properties.



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