Due to cyclic freezing-thawing and drying-wetting, cracks are commonly encountered in loess regions and adversely affect the seepage and stability of slope engineering. However, the influences of freeze-thaw (FT) cycles on desiccation cracking of intact loess are rarely known. In this study, evaporation tests were performed on an intact loess with different water contents and subjected to various numbers of FT cycles. To interpret the desiccation cracking behavior, the microstructure of tested intact loess was determined by conducting the scanning electron microscope (SEM) tests. Results show that FT cycles further enhance the inherent loose structure of intact loess through pore expansion, pore connection and formation of continuous channel, and destroy the particle bonding contributed by fine particles and cementitious minerals. The intact loess subjected to 0 FT cycle predominately exhibit single cracks, while both single and Y-shaped cracks are observed in intact loess subjected to non-zero FT cycles. The difference in crack pattern is attributed to the enhanced loose structure owned by the latter, which forms a large number of structural defects. Furthermore, the crack ratio and the average width and total length of cracks increase with the increasing numbers of FT cycles. This can be attributed to the two effects induced by FT cycles, one is the degradation of tensile strength due to bonding breakage, and the other is the inhomogeneous shrinkage deformation due to the rapid evaporation of water in specimens with enhanced loose structure. Furthermore, the FT cycles cause more significant effects on the desiccation cracking of intact loess with higher water contents than those of intact loess with lower water contents, primarily due to the larger frost heaving forces induced in the former.

中文翻译：

---

冻融循环对完整黄土干燥开裂的影响


由于循环冻融和干湿作用，黄土地区经常出现裂缝，对边坡工程的渗流和稳定性产生不利影响。然而，冻融 （FT） 循环对完整黄土干燥开裂的影响鲜为人知。在这项研究中，对具有不同含水量的完整黄土进行了蒸发测试，并进行了不同次数的 FT 循环。为了解释干燥开裂行为，通过进行扫描电子显微镜 （SEM） 测试确定了测试完整黄土的微观结构。结果表明，FT循环通过扩孔、孔隙连接和连续通道的形成进一步增强了完整黄土固有的疏松结构，破坏了细颗粒和胶凝矿物贡献的颗粒结合。受 0 FT 循环影响的完整黄土主要表现为单裂缝，而在受非零 FT 循环影响的完整黄土中，同时观察到单裂缝和 Y 形裂缝。裂纹模式的差异归因于后者拥有的增强的松散结构，从而形成大量的结构缺陷。此外，裂纹率以及裂纹的平均宽度和总长度随着 FT 循环次数的增加而增加。这可以归因于 FT 循环引起的两个效应，一个是由于粘合断裂而导致的拉伸强度下降，另一个是由于具有增强的松散结构的试样中由于水分的快速蒸发而导致的不均匀收缩变形。 此外，FT 循环对含水率较高的完整黄土的干燥开裂的影响比含水率较低的完整黄土的干燥开裂更显着，这主要是由于前者引起的冻胀力较大。