Soil Stabilization Stops Pavement Settlement Above Culvert in Pennsylvania

Problem

In Huntington County, Pennsylvania, there is a section of McAlevy Fort Road that lies north of a precast box culvert bridge. The Pennsylvania Department of Transportation (PennDOT) identified this section of road as chronically settling over time, and deployed maintenance crews to add cold patch periodically as a temporary fix. After seven years of these patches, PennDOT performed a tracer dye test and determined the underlying cause of settlement was a misdirected drainage channel entering a nearby creek. PennDOT then redirected the drainage channel, but after so many years of erosion, PennDOT needed a way to permanently fix the compromised foundation soils left behind.

Analysis

URETEK performed Dynamic Cone Penetrometer (DCP) tests on the soils, and with readings of five blows or fewer at various depths, they determined that void areas and weak soils were left behind from water erosion beneath the roadway. It was clear that these void spaces and weak soils were the cause of the ongoing settlement issues PennDOT had been dealing with.

Solution

URETEK chose to employ its URETEK Deep Injection® (UDI) process to fill voids and strengthen the foundation soils at depths of four, eight, and 12 feet. Over roughly 20 hours, URETEK 486 Star® Polymer was injected into the weak foundation soils. Clean up took place in a matter of minutes, and the URETEK crew departed the work site leaving behind a fully-functional roadway.

Result

URETEK achieved stabilization of the weak foundation soils through UDI, offering PennDOT a permanent solution to a chronically settling section of road. Never satisfied with the bare minimum, however, the URETEK team also raised settled pavement on the south side of the culvert back to grade to offer a smoother ride until it could be milled and overlaid.

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.