In Henderson, Tennessee, a hospital office building had experienced settlement across half of the building; about 160’ x 50’. The existing structure is supported by drilled shafts extending into solid rock. The slab, however, is supported by 30’ plus of backfill material. Consolidation of the backfill material had caused slab settlement and voids, creating trip hazards for patients and health care workers throughout the facility. With the safety of surrounding personnel compromised, URETEK was called to rectify the settlement issue.
A local consulting firm completed a geotechnical exploration to evaluate the condition of underlying soils. The slab was cored in 12 locations to evaluate the subgrade soils. The study detected weak soils and several voids as large as 1.5” below the slab. URETEK Deep Injection® (UDI) and URETEK Method Injection were proposed for the project as a quick and effective way to stabilize the underlying soils while providing a lift to the settled slab.
For the slab settlement project in Henderson, UDI combined with Method was the ideal solution to lift the slab back to grade and stabilize the soils below. During the repairs, URETEK crew performed the Method Process in a grid pattern across the compromised area. UDI was used to stabilize and fill voids along an external grade beam. Crewmembers injected URETEK 486 Star® polymer into the subgrade soils according to a site-specific injection plan. This both stabilized the weak fill soils and filled all voids to ensure that the slab’s bearing capacity requirements were met.
UDI stabilized the slab, increased the compressive strength of the soils below, and improved safety of hospital personnel. The owner was pleased with the result. Settled slabs were lifted back to grade to alleviate tripping hazards. The repair was completed at night to avoid downtime for the tenants, and all flooring and furniture were left in place during the installation. The tenants were able to work during the day between the crews’ night shifts. Thanks to URETEK, the operation was completed ahead of schedule and with no downtime for the tenants.
URETEK Deep Injection® (UDI)
Widely referenced throughout the 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. 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.