Abstract Freeze-thaw induced change in the strength behaviour of the underlying loess is an important cause of the instability of artificially excavated and natural loess slopes. The loess is mostly in a true triaxial stress state, which was rarely considered in previous strength tests. This study explored the effect of freeze-thaw cycles on the strength behaviour of recompacted loess under true triaxial stress and its relationship with the meso-structure by carrying out freeze-thaw tests, true triaxial tests and scanning electron microscope (SEM) tests. Freeze-thaw cycles exhibit little effect on the shape of the stress-strain curves of recompacted loess, while more significant changes were observed with different b-values. The shear strength first decreases with freeze-thaw cycles and then increases to a constant after five cycles, while it continues to decrease with the b-value. For strength parameters, the cohesion decreases after freeze-thaw and tends to stabilize after five cycles while the internal friction angle is less affected. As the b-value grows, the cohesion first grows and then declines, with the peak value at b = 0.5 while the internal friction angle varies within a narrow range (28.11° - 32.53°). The effect of freeze-thaw on the shape of the failure surface for recompacted loess on the π plane is negligible but pronounced on the size of the failure surface. SEM images and the specimen size imply that the structure of recompacted loess tends to be loose after freeze-thaw cycles, corresponding to a greater pore area ratio and the decrease in the cohesion. Moreover, both the orientation and circularity of soil particles show limited changes, which reveals the insignificant change in the internal friction angle with freeze-thaw

中文翻译：

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真三轴试验中冻融循环对再压实黄土强度行为的影响

摘要 冻融引起下伏黄土强度行为的变化是人工开挖和天然黄土边坡失稳的重要原因。黄土多处于真三轴应力状态，这在以往的强度试验中很少考虑。本研究通过冻融试验、真三轴试验和扫描电子显微镜（SEM）试验，探讨了冻融循环对真三轴应力下再压实黄土强度行为的影响及其与细观结构的关系。冻融循环对再压实黄土的应力-应变曲线形状影响不大，而不同b值的变化更为显着。剪切强度首先随着冻融循环而降低，然后在五个循环后增加到一个常数，同时随着 b 值的增加而继续减小。对于强度参数，内聚力在冻融后下降，并在五个循环后趋于稳定，而内摩擦角的影响较小。随着 b 值的增加，内聚力先增加然后下降，峰值在 b = 0.5 处，而内摩擦角在一个狭窄的范围内（28.11° - 32.53°）变化。冻融对再压实黄土在 π 平面上的破坏面形状的影响可以忽略不计，但对破坏面的大小影响显着。SEM 图像和试样尺寸表明，再压实黄土的结构在冻融循环后趋于松散，对应于更大的孔隙面积比和内聚力的降低。此外，土壤颗粒的方向和圆形度都表现出有限的变化，