Abstract: Weak expansive soil after treatment with waterproof and moisturizing can be used as the highway subgrade filling, and studies on its dynamic response characteristics are few. For a thorough analysis of the dynamic properties of weak expansive soil in Hefei, a series of cyclic load triaxial tests was conducted. Considering the influence of confining pressure, consolidation ratio and dynamic stress amplitude on the weak expansive soil dynamic property, the tests obtained the development curves of the accumulated deformation and dynamic strength under different test conditions. Based on the accumulated deformation of samples under different confining pressures, consolidation ratios and dynamic stress amplitudes, a prediction model for accumulated deformation of weak expansive soils was established. The accumulated strain curves of expansive soils can be divided into plastically stable, critical and destructive types according to the strain rate, and the criteria for judging the cumulative strain of weak expansive soil was given. The dynamic strength of weak expansive soil under different confining pressures and consolidation ratios was analyzed. It was found that the dynamic strength of the soil decreased a lot when the consolidation ratio was over than 1.5; the dynamic cohesion cd decreased with the increase of failure vibration, and the dynamic internal friction angle ?d decreased slightly with the increase of failure vibration. Results obtained can provide basic data and reference for relevant projects.

Key words: expansive soil, cyclic loading, consolidation stress ratio, accumulated deformation, dynamic strength