冻融作用下复合相变材料改良黄土力学特性研究及机理分析∗

为降低冻融作用对黄土力学性能的劣化影响，基于相变材料的温度调控功能，提出了一种采用膨胀石墨?正十四烷复合相变材料（EG?C₁₄）改良黄土的方法。以兰州黄土为研究对象，开展典型冻融循环后不同 EG?C₁₄掺入比黄土试样的体积变形试验、力学性能试验和微观结构试验，探究冻融作用下不同 EG?C₁₄掺量对黄土力学性能的影响规律及改良机理。试验结果表明：EG?C₁₄减缓了冻融循环过程中土体内部的温度变化，进而有效抑制了土体的胀缩变形；同时，EG?C₁₄降低了冻融循环对土体微观结构的损伤，与素黄土相比，多次冻融循环后改良土体内部的支架孔隙明显减少，颗粒骨架也更为密实，进而增强了土体的力学性能；此外，EG?C₁₄ 改良黄土的力学性能随 EG?C₁₄掺量的增加先增大然后逐渐趋于稳定，且掺量为 4% 时改良效果最佳。

Study on the Mechanical Properties and Mechanism Analysis of Loess Improved by Composite Phase Change Materials under Freeze‑thaw Conditions

To mitigate the detrimental impact of freeze-thaw cycles on loess mechanical properties, a method using expanded graphite-n-tetradecane composite phase change material (EG-C₁₄) was proposed, leveraging the temperature modulation capability of phase change materials. Focusing on the Lanzhou loess, a series of tests were conducted after typical freeze-thaw cycles, including volumetric deformation tests, mechanical property tests, and microstructure tests on loess samples with varying EG-C₁₄ dosage levels. The study aimed to explore the influence of different EG-C₁₄ dosages on loess mechanical properties under freeze-thaw conditions and its enhancement mechanism. Results indicate that EG-C₁₄ effectively mitigated the temperature variations within the soil during freeze-thaw cycles, thereby suppressing soil expansion and contraction deformation. Additionally, EG-C₁₄ minimized soil microstructure damage during freeze-thaw cycles. Enhanced soil exhibited reduced scaffold porosity and denser particle skeleton compared to untreated loess after multiple cycles, thus improving its mechanical properties. Furthermore, EG-C₁₄ dosage positively correlated with enhanced mechanical properties, stabilizing notably at a 4% dosage. These findings offer valuable insights for deploying EG-C₁₄ enhanced loess in practical applications.