Flexible pavement sections constructed over expansive soil deposits often undergo significant damage due to volume changes in the underlying soil strata. When expansive soil deposits are confined to shallow depths, conventional rehabilitation methods can be pursued. However, such treatment strategies become impractical for expansive soil deposits deeper than 1 m from the pavement surface. In such cases, alternative remedial measures are needed to dissipate the soil-generated swelling stresses. A recently completed research study investigated the differential heaving problem along a roadway segment near the Idaho–Oregon border. Laboratory characterization of soil samples indicated the presence of highly expansive soils up to depths of 7.6 m from the pavement surface. The current study focused on evaluating the suitability of a high-density polyurethane (HDP) grout injection as a potential remedial measure for this pavement section. Laboratory testing of unbound materials treated with HDP indicated significant improvements in resilient modulus and shear strength properties. Finite element modeling of the problematic pavement section indicated that, depending on the treated layer thickness, the differential heave magnitude can be reduced significantly.