Cumulative plastic deformation of subgrade fine-grained soil under intermittent cyclic loading and its prediction model

There is a time interval between adjacent trains in the railway line in service, thus the long-term loading of trains on the subgrade is composed of the vibrational loading when the train is passing and the intermittent loading when train passed away, namely the intermittent cyclic loading. A series of dynamic triaxial tests with continuous loading and intermittent loading (single-stage and multi-stage) was conducted to study the deformation of subgrade under the intermittent cyclic loading of trains. The cumulative plastic strain under intermittent loading was studied, and the prediction models were proposed. Results show that the resistance of the sample to cyclic loading was improved and the cumulative plastic strain was reduced due to the loading intermittence. The cumulative plastic strain showed "phased growth" under intermittent loading instead of the "smooth growth" under the continuous loading. Finally, the hyperbolic model based on the time-hardening approach could better predict the cumulative plastic strain of the stable and critical samples under intermittent loading. The research can provide guidance for further understanding of the deformation characteristics and settlement prediction of railway subgrade.