Study on the physical and mechanical properties of recycled weathered rock materials in expressway subgrade in permafrost areas

Abstract

In view of the specialized climatic conditions in high-cold and high-altitude regions, the direct, repeated freeze-thaw and freezing processes resulting from diurnal and seasonal temperature changes pose a significant threat to the integrity of the roadbed stones in these areas. Weathering and fragmentation constitute a form of rock damage. Rock damage negatively impacts the air convection within the rock subgrade, rendering it incapable of safeguarding frozen soil. The objective of this study is to investigate the mechanical properties and the constitutive model for freeze-thaw damage of three recycled weathered rock materials subjected to varying freeze-thaw cycles. Additionally, it aims to examine the damage and degradation mechanism of recycled weathered rock materials under the combined influence of freeze-thaw and load. The model is then employed to validate the experimental data. Research indicates that with an increase in the number of freeze-thaw cycles, the quality of the three types of recycled weathered rock samples exhibits a gradual decrease, accompanied by a corresponding reduction in P-wave speed. The elastic modulus and compressive strength of the three recycled weathered rock materials show an increase with rising confining pressure and a decrease with a growing number of freeze-thaw cycles. The types of damage include splitting and shear damage. The presented damage model can elucidate the pattern of damage evolution in the specimen under varying confining pressures and freeze-thaw cycles. The expansion of internal micro-cracks is influenced differently by freeze-thaw cycles and loads; moreover, the coupling effect of damage exhibits pronounced nonlinear characteristics. Substantiated by experimental results, the damage constitutive model demonstrates both reasonability and feasibility.