A New Stress–Strain Curve Prediction Model for Moraine Soil Under Freeze-Thaw Cycles Considering Mechanical Degradation Characteristics

Abstract

The stress-strain behavior of remolded moraine soils is highly sensitive to freeze-thaw (F-T) cycles. However, studies on the evolution of the stress-strain curve and microstructure in remolded moraine soils under F-T cycles remain limited. To address this gap, a comprehensive experimental program was conducted that included F-T cycle tests, triaxial shear tests (TST), and micro-CT scanning to examine the influence of F-T cycles on a remolded moraine soil from Linzhi City, Xizang. In addition, a novel Duncan-Chang-Jiang-Lu (DC-JL) model has been proposed in this study to fit and predict stress-strain curves. The results show that F-T cycles cause a marked reduction in shear strength (TSS) and the initial average elastic modulus (E₀) following softening and a hyperbolic bulge failure mode. TSS decreases by 12%∼30%, and E₀ decreases by 30%∼45%. The DC-JL model reliably predicts stress-strain curves for any F-T cycle within the experimental range (N = 0–20) using results from N = 0, 2, 5, 10, and 20 cycles. Furthermore, the residual strength provided by the DC-JL model closely matches the experimental data. F-T cycles significantly impact mechanical behavior by deteriorating the internal microstructure, increasing micro-porosity (from 14.25% to 18.69%), and leading to the formation of numerous cracks. The findings of this study are not only valuable for a better understanding of freeze-thaw degradation in moraine soils but also for assessing long-term stability using the proposed new model.