Performance evaluation and stabilization mechanism of red clay treated with polyurethane

Red clay, a widely distributed soil, weakens significantly when exposed to water. This poses challenges for using it as a foundation for urban infrastructure, as rainwater scouring, infiltration, and external loads can cause uneven settlement and landslides, compromising structural integrity. To address this issue, we propose the use of a green highly permeable water-soluble polyurethane material (PSP) as an alternative to conventional curing agents. We conducted a series of tests to evaluate the efficacy of PSP in improving the mechanical properties of red clay. Acoustic emission tests were used to examine the failure mode of PSP-stabilized red clay, while scanning electron microscopy provided microscopic insights into clay stabilization mechanisms. The triaxial test results establish empirical relationships between strength, stiffness, toughness, and control parameters (PSP content, moisture content, and confining pressure) of the stabilized clay. We found that PSP-stabilized soils exhibit ductile failure and strain hardening, with PSP curing agents effectively enhancing clay strength and stiffness within a 3-day curing period. Univariate analysis reveals positive correlations between peak energy absorption values, peak stress rates, and PSP content, while showing a negative correlation with moisture content. Confining pressure variations have relatively little effect on peak stress ratios of PSP soils, and PSP soil stiffness minimally influences confining pressure as PSP content increases. Importantly, PSP treatment significantly increases ductility compared to untreated clay soils, distinguishing PSP soils from hydric soils. •Microscopic strengthening mechanism of PSP-treated red clay soils.•The relationship between failure mode, mechanical properties, PSP content and moisture content is analyzed.•The empirical formulas for estimating peak stress, initial tangent modulus and failure ratio are established.•A solution for the rapid trenchless curing of clay is presented.