The expansion and mechanical property-based cavity expansion model for polyurethane grouting underneath the airport pavement

Abstract

The cavity beneath the pavement will be further expanded by the self-expansion pressure of polyurethane foam after grouting, leading to a decline in its density and mechanical properties of the polyurethane foam. This study proposed a cavity expansion model that coupled the influence of expansion characteristics of polyurethane foam and the mechanical behavior of surrounding soil, thus, the cavity expansion performance with declining expansion pressure and changing mechanical parameters in confined soil and pavement was accurately characterized. The study sequences are as follows: (1) a series of confined expansion tests and uniaxial compression tests were conducted via a self-developed device under various densities and material ratios of the polyurethane foam, thus the prediction formula of expansion pressure with material ratio and density was obtained, and the variation of the ultimate compressive strength and elastic modulus of polyurethane foam can also be quantified; (2) a cavity expansion model considering the decrease of expansion pressure and compressive strength of polyurethane foam during the expansion was proposed based on the combination of the conventional cavity expansion model and the conducted expansion test results; (3) the parametric analysis was conducted to investigate the influence of the initial density (ρ0, refers to the density when the self-expansion pressure starts to apply on the surrounding soil), material ratio of polyurethane foam and the original cavity size on the expansion radius, so the evolution of mechanical properties after cavity expansion under the pavement was revealed based on the density change after expansion (ρ). The feasibility of the improved model for the expansion of polyurethane foam in soil was evaluated in this study, which can provide a reference for the design and optimization of a polyurethane foam filling scheme for the cavity underneath a pavement.