Physical and Mechanical Properties of Expanded Polystyrene (EPS) Particle Lightweight Soil under Freeze–Thaw Cycles

[Image: see text] In seasonally frozen regions, the bearing capacity of soil decreases and gradually deteriorates after undergoing freeze–thaw cycles. To resolve this problem, based on the idea of frost-resistant filling materials, a filling scheme of expanded polystyrene (EPS) particles lightweight soil in cold regions was proposed. Unconfined compressive strength, direct shear, and micro-SEM tests were carried out to study the physical and mechanical properties of EPS particles lightweight soil under freeze–thaw cycles. The results indicate that the EPS particle lightweight soil has good frost resistance and can be used as frost-resistant filling material in cold regions. Under freeze–thaw cycles, EPS particle lightweight soil maintains good integrity; EPS particles can effectively reduce the frost heave rate, mass loss rate, and compressive strength loss rate of lightweight soil. The compressive strength depends on the EPS and cement contents: it decreases with an increase in the EPS content and increases with an increase in the cement content. The strength loss rate decreases with an increase in both. When the content of EPS is larger (more than 2%), the soil cement bound with EPS particles is limited, and the performance of lightweight soil decreases. The shear strength and cohesion decrease with an increase in freeze–thaw cycles and EPS content, and the internal friction angle follows no obvious rule with regard to the increase in freeze–thaw cycles but decreases with an increase in the EPS content. Based on the experimental results, an empirical formula for the compressive strength of EPS particle lightweight soil under freeze–thaw cycles was proposed. This study can provide a reference for the engineering design and application and provide new ideas for resolving freeze–thaw problems in construction engineering in cold regions.