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

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

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-C_(14))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-C_(14)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-C_(14)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-C_(14)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-C_(14)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-C_(14)改良黄土的力学性能随EG-C_(14)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。

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-C_(14))was pro-posed,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-C_(14) dosage levels.The study aimed to explore the influence of different EG-C_(14) dosages on loess mechanical properties under freeze-thaw conditions and its enhancement mechanism.Results indicate that EG-C_(14) effectively mitigated the temperature variations within the soil during freeze-thaw cycles,thereby suppressing soil expansion and contraction deformation.Additionally,EG-C_(14) 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 me-chanical properties.Furthermore,EG-C_(14) dosage positively correlated with enhanced mechanical prop-erties,stabilizing notably at a 4%dosage.These findings offer valuable insights for deploying EG-C_(14) enhanced loess in practical applications.