Mechanical behaviors of frozen clay under dynamic cyclic loadings with freeze-thaw cycles

Abstract

This paper presents a comprehensive research about the coupled influence of freeze-thaw procedure and stress condition on cyclic mechanical properties of the frozen clay. According to cyclic test data of frozen clay at the temperature −10 °C, dynamic responses in various cases of confining pressures, cyclic loading amplitudes and freeze-thaw cycles are investigated in detail. Cyclic stress ratio is used to investigate the coupling effects of the freeze-thaw procedure, confining pressure and dynamic loading amplitude on permanent strain curves under same dynamic cycle-time. The permanent axial strain raises with increase of cyclic stress ratio. An empirical formula is presented to quantitatively characterize the coupled effects on the permanent deformation of frozen samples. Two-stage evolution features of resilient modulus in the cyclic loading process are clearly observed under all confining pressures and dynamic stress amplitudes. The inflection points of two-stage curves are rationally considered as the endpoints for the post-compaction compression stage. The axial strain value at this inflection point is defined as the yield strain under cyclic loading conditions. The yield strain point roughly occur around 3000th-3900th loading cycles. When the freeze-thaw cyclesreached at 6, the loading cycles at the inflection point (yield point) were approximate 3300. There was no obvious freeze-thaw cycle threshold for the dynamic elastic properties of frozen samples. Finally, based on the analysis for the loading cycle numbers at those yield points, the dynamic strength curves of samples under different confining pressures can be established.