Cumulative deformation prediction and microstructure change of coarse-grained soil under cyclic loading

This research aims to reveal the macroscopic cumulative deformation development pattern and internal structural change characteristics of coarse-grained soils under moving vehicle loads. Dynamic triaxial tests are used to investigate the development of cumulative deformation of coarse-grained soils under various deviatoric stresses, moisture contents, and loading frequencies. Based on the results of indoor tests, a comprehensive prediction model for the cumulative deformation of coarse-grained soils was established. The cumulative deformation increases with the increasing deviatoric stress, moisture content, and loading frequency. As the deviatoric stress grows, the cumulative deformation rate increases correspondingly. The cumulative deformation prediction model for coarse-grained soils proposed in this study has high accuracy. Cyclic loading reduces the number of large pores, increases the number of smaller pores, and increases the proportion of micropores with increasing deviatoric stress and moisture content. The effect of loading frequency on the deformation of coarse-grained soils is relatively small but still not negligible. Cyclic dynamic loading can transform the long pores in coarse-grained soil subgrade filler into elliptical and circular pores. The increase in moisture content can increase the proportion of long pores in coarse-grained soil filler. This research can deliver a valuable reference for analyzing the cumulative deformation of coarse-grained soils subjected to cyclic loading.