Abstract: The unconsolidated undrained triaxial shear tests are carried out to explore the stress-strain relationship behaviors of unfrozen silty sand under different freeze-thaw cycles. Based on the test results, when the confining pressure is low, both the unfrozen silty sand or the silty sand experiencing fewer freeze-thaw cycles exhibits weak strain softening phenomenon; And stain of silty sand will change from weak stain softening to stain hardening after experiencing a certain number of freeze-thaw cycles. No matter the unfrozen silty or the frozen silty shows strain hardening under a higher confining pressure level, their stress-strain curves are both the typical hyperbola. and the normalization of the stress-strain relationship is vital to study the stress-strain properties. In this paper, four kinds of common normalization factors, which are widely adopted for unfrozen soil to study stress-strain characteristics as well as the corresponding normalized conditions, are introduced. Based on the normalization factors above, a new normalized factor is proposed to analyze the stress-strain relation of soils under freeze-thaw cycles and the normalized conditions are defined. A new normalized stress-strain equation is established to predict the stress-strain curve of silty sand under freeze-thaw cycles and confining pressures. Comparison of the prediction and test results shows that the established predict model can consider the influences of freeze-thaw cycles and has better fitting and prediction accuracy.

Key words: freeze-thaw cycle, silty sand, stress-strain relationship, strain hardening, normalized factor