A novel evaluation method for accumulative plastic deformation of granular materials subjected to cyclic loading: Taking frozen subgrade soil as an example

Abstract

This paper presents multi-stage cyclic loading tests with three confining pressures and eight dynamic stress amplitudes on frozen subgrade soil at the negative temperature − 2 °C to experimentally study accumulative and resilient deformation properties under different cyclic loadings. The coupled effects of the confining pressure and dynamic stress amplitude on accumulative and resilient deformation properties of frozen sample are analyzed in detail. Accumulative and resilient deformation behaviors of frozen samples at each stage of multi-stage cyclic loading tests exhibit similar patterns as that observed in the single-stage cyclic loading tests. Two-stage evolution feature for resilient modulus of frozen subgrade soil is experimentally determinated. Critical cyclic number is defined as the turning point of two-stage feature for resilient modulus to further distinguish the post-compaction compression stage and secondary cyclic compression stage of frozen subgrade soil. The influence of confining pressure on critical cyclic number is negligible. With the increase of dynamic stress amplitude, critical cyclic number approximately increases. Dynamic stress amplitude, rather than confining pressure, is main influencing factor for critical cyclic number in this investigation range of confining pressure. A new evaluation criterion for three typical deformation areas of granular materials subjected to cyclic loading is proposed based on the shakedown theory. The devlopment features of accumulative permanant strain at the multi-stage cyclic loading tests are studied and judged by two published shakedown criteria and presented new criterion. Two published shakedown criteria's applicability and limitation for frozen subgrade soils are further investigated and discussed. The assessment capacity of this new criterion is validated by all testing results for frozen subgrade soils. The evaluation results based on this new criterion are in approximate agreement to those according to Chen's shakedown criterion (Chen et al., 2019).