Study on the State Evolution and Long-Term Stability Control of Subgrades

Abstract

As highway engineering in China shifts from large-scale construction to long-term maintenance, the influence of long-term subgrade stability on pavement service performance has become increasingly prominent. Current construction control practices mainly rely on stage-specific indicators such as the degree of compaction, which cannot fully capture the continuous evolution of subgrade conditions under traffic loading, moisture fluctuations, wetting–drying cycles, and freeze–thaw actions. From a life-cycle perspective, this paper analyzes the relationships among compaction state, moisture condition, and mechanical response, and discusses the effects of key parameters-including degree of compaction, porosity, water content, degree of saturation, matric suction, and resilient modulus-on subgrade performance. The study suggests that subgrade stability is jointly governed by fill material properties, compaction energy, moisture migration, particle rearrangement, and cumulative loading effects. Future evaluation should shift from single-index control based on compaction degree toward a coordinated assessment using multiple state parameters, thereby providing a basis for subgrade distress diagnosis, performance prediction, and maintenance decision-making.