Effect of Waste Tire Particle Content on the Compressive Behavior and Pore Structure of Loess Subgrade Materials

In response to the challenges of low recycling rates of waste tires and their underutilization in loess subgrades, this study systematically investigates the compression deformation characteristics of tire particle (4-6 mm)-modified loess through comprehensive laboratory testing. Using one-dimensional compression tests and cyclic loading-unloading tests, the effects of different tire particle contents (0% to 100%) on pore structure evolution, compression parameters-including the compression coefficient, compression modulus, and volumetric compression coefficient-and deformation mechanisms were thoroughly analyzed. The study reveals critical state characteristics and deformation mechanisms of tire-derived aggregate-loess mixtures (TDA-LMs) and establishes a predictive model for their compression behavior. The research results indicate the following: (1) The compression behavior of TDA-LM exhibits a distinct dosage threshold and stress dependence: the critical blending ratio is 30% under stresses below 100 kPa, increasing to 40% at higher stresses (≥100 kPa); (2) Mixtures with medium to low tire content display strain hardening, whereas pure tire specimens show approximately 10% modulus softening within the 200-300 kPa range. Stress- and content-dependent models for the compression modulus and volumetric compression coefficient were developed with high accuracy (R² > 0.96); (3) The dominant deformation mechanism shifts from soil skeleton plastic yielding (at tire contents < 40%) to rubber-dominated elastic deformation (at contents > 50%). Over 85% of cumulative deformation occurs during the initial loading phase, indicating that particle-soil interface restructuring primarily takes place early in the loading process. This study provides a theoretical basis and practical design parameters for the application of waste tires in loess subgrade engineering, supporting the sustainable reuse of solid waste in environmentally friendly geotechnical construction.