I-95 Settlement Corrected in Cranston, Rhode Island
Problem
In Cranston, Rhode Island, a section of I-95 North was experiencing up to two inches of settlement under an area of pavement that transversely impacted all lanes and extended for a total linear distance of 170 feet. The original highway design included up to four inches of asphalt over concrete. However, over time as much as three feet of asphalt patch material had been applied to lanes that exhibited the greatest settlement issues, with varying amounts of asphalt patch applied across all lanes. A bearing capacity issue and possible sinkhole issue were both suspected, and Rhode Island DOT officials called URETEK.
Analysis
The location of the I-95 settlement corresponded with the location of a 108-inch diameter RCP storm line originally installed four to five feet beneath the pavement structure and running the full 170-foot length of the visible settlement area. Additionally, two 12-inch diameter underdrains were installed on either side of the main RCP storm line. Third party engineers conducted boring tests and various analyses, but RIDOT officials were left without a clear indication of the cause of the main lane I-95 settlement issue. In the end, it was suspected that the surface settlement issues resulted from fines being taken into the clogged and non-functioning underdrain system.
Solution
URETEK developed an injection plan that would stabilize and strengthen the foundation soils down to 15 feet below grade and presented the plan with engineering drawings to RIDOT. The key to the plan would be a precise application of URETEK Deep Injection® (UDI) to stabilize the soils down to the underdrains and address the settlement issues present on I-95. The URETEK crew drilled host holes to depths determined through Dynamic Cone Penetrometer (DCP) testing conducted in each surface lane. URETEK then bridged the identified weak soils at depth with injections spanning the area of settlement and extending into areas of identified good soils.
Result
With no excavation and no lane closures during high-volume traffic times, URETEK crews completed the project in just 10 days – five days sooner than estimated – at a final cost $125k under budget. URETEK successfully stabilized the foundation soils down to the compromised underdrains for the full length of the approx. 170 linear feet, and transversely across Rhode Island’s main highway artery I-95 North for 24 feet. The URETEK crew injected five different elevations below the surface, stabilizing the soils and creating a wall of protection that prohibited fines from being taken into the failed underdrains. At the end of the project, the soil bearing capacity was increased and the risk of future sinkhole development was significantly mitigated.
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.
