Long-term characterising plastic behavior of thawed subgrade clay under cyclic loads

The effects of the number of freeze-thaw cycles was used the method of indoor test and the stress level on the static shear strength and plastic deformation soil were investigated. The results show that the static shear strength decreases with the decrease of confining pressure and the accumulation of freeze-thaw cycles， and the permanent deformation gradually develops from plastic stability to plastic creep or incremental instability when the dynamic stress level increases. Based on the comprehensive analysis of the test results，the critical stress level to avoid the instability of permanent deformation and the discrimination criteria of each type are defined，a description formula of critical dynamic stress considering confining pressure and freeze-thaw cycles is proposed，and the ratio of shear stress generated by dynamic stress to shear strength is used to represent shear action，and a mechanical-empirical model suitable for permanent deformation of subgrade clay subjected to freeze-thaw cycles was established and verified. The results of the study can provide theoretical support for the stability and durable operation of the subgrade in the monsoon freeze zone. © 2023 Editorial Board of Jilin University. All rights reserved.