Impact of density on geotechnical engineering characteristics of high-expansive polyurethane foam

Ground deformation induced by stress transfer from civil engineering structures often leads to settlement issues, impacting the performance of structures like roads, parking slabs, and factory floors. Polyurethane (PU) foam, known for its significant volumetric expansion, emerges as a potential solution to mitigate settlement problems. However, a comprehensive understanding of the geotechnical engineering properties of PU foam is crucial for effective design and injection work planning. This study focuses on a two-component PU foam composed of polyol and isocyanate, evaluating various geotechnical properties across different foam densities. Test samples were prepared by injecting PU foam into a vertical PVC cylinder to lift an internal piston. Key properties assessed include compressive strength ( ), secant modulus ( ), secant Poisson’s ratio ( ), cyclic residual strain ( ), yield vertical stress ( ), compressibility indices, and coefficient of permeability ( ). Results show an increase in ,   , , and  with rising foam density, while , compressibility indices, and  decrease. Additionally, at constant foam density,  decreases with higher vertical stress, and  increases with cyclic stress ratio ( ) and the number of cycles ( ). Regression analyses yield empirical formulas for predicting these properties, providing valuable insights for the utilization of PU foam in geotechnical applications.