Feasibility Study of Quantifying the Soil Strength Improvement from Polyurethane Injection

Polyurethane (PU) injection is an innovative soil stabilization method used for ground improvement and foundation remediation, particularly in mitigating settlement issues and enhancing soil properties. However, predicting the increase in soil strength after injecting with PU is challenging due to the complex mechanisms through which PU interacts with the injected soil. This paper presents the initial results from investigating these mechanisms and the resulting increase in soil shear strength. A large-scale shear box (50 cm × 1,000 cm × 66 cm) was used to perform direct shear testing on sand with and without PU injection. One-component and one two-component polyurethanes were used in this study. The paper presents limited initial results showing the increase in the shear strength of the polyurethane-grouted sands. While the limited results cannot be conclusive for quantifying increase in strength, the main contribution is providing a pathway to measure the increase in strength of grouted sands on a large scale, when only a percentage of the sand is grouted, and the grout is not uniform. The results highlighted the different mechanisms polyurethane grouts can help improve the strength of the sand, despite the difference in the properties and grouting mechanisms between the two polyurethane grouts used.