唐少容^a,b,c, 杜 鹏^a, 李昊天^a, 殷 磊^a

(宁夏大学 a. 土木与水利工程学院, b. 宁夏节水灌溉与水资源调控工程技术研究中心,c. 旱区现代农业水资源高效利用教育部工程研究中心, 宁夏 银川 750021)

引用格式:

唐少容, 杜鹏, 李昊天, 等. 由石蜡基相变材料和煤渣改良的粉砂土的冻融性能[J]. 中国粉体技术, 2024, 30(1): 123-131. 

TANG S R, DU P, LI H T, et al. Freeze-thaw properties of silty sand modified by paraffin-based phase change materials and cinder[J]. China Powder Science and Technology, 2024, 30(1): 123-131.

摘要:【目的】针对季节冻土区渠道的衬砌结构因冻融作用而受损的现状,同时为了解决石蜡基相变材料( phase changematerials,PCM)的泄露,并满足煤渣的再利用需求,研究石蜡基 PCM 和煤渣对土体冻融性能的影响。 【方法】以粉砂土为研究对象,选取石蜡基 PCM 和煤渣作为改良剂,制备石蜡基 PCM 改良土和石蜡基 PCM-煤渣改良土;通过冻融循环作用下的体积变化率试验、 无侧限抗压强度试验,微观结构及潜热研究土体的体积和无侧限抗压强度的变化。 【结果】石蜡基 PCM 能抑制粉砂土的冻融变形,质量分数为 8%时 2 种改良土的体积变化率最小;随着冻融循环次数的增加,土体的无侧限抗压强度均降低,降低速率先大后小;循环次数相同时,加入煤渣的改良土的无侧限抗压强度均大于未加入煤渣的;冻融循环 9 次后,石蜡基 PCM 质量分数为 10%的石蜡基 PCM 改良土的无侧限抗压强度最低;2 种改良土的结构比粉砂土更密实、稳定;潜热的吸收或释放延缓了土体冻融过程。 【结论】将石蜡基 PCM 和煤渣共同掺入粉砂土,能控制土体的冻融变形且效果稳定,改善土体的冻融性能,减轻季节冻土区输水渠道衬砌结构的冻害,提高煤渣的利用率。

关键词: 石蜡基相变材料; 煤渣; 改良土; 粉砂土; 冻融性能

Abstract

Objective In view of the current situation the lining structure of farmland water transmission channel is frequently damaged due tofreeze-thaw cycles in areas with seasonal frozen soil. To solve the leakage problem of paraffin-based phase change materials (PCM) and meet the recycling demand of cinder in local thermal power plants, paraffin-based PCM and cinder are added into the channel soil as additives and the primary focus is on studying the mechanism of improving the freeze-thaw performance of soil. Additionally, the impact of the latent heat effect of paraffin-based PCM on temperature field within seasonally frozen soil is also analyzed.

Methods The silty sand collected from a channel in Ningxia was used as the research object. Paraffin-based PCM and cinder were selected as the improver to prepare two distinct types of improved soil: paraffin-based PCM improved soil and paraffin-based PCM -cinder improved soil. Through the volume change rate test and unconfined compressive strengh test under the freeze - thaw cycle, the volume change rate and unconfined compressive strength of silty sand and the improved soil were analyzed. Besides, an analysis of the microstructure and latent heat changes of the improved soil before and after the freeze-thaw cycle was also conducted. This comprehensive approach allowed for a thorough investigation into the combined effects of paraffin-based PCM and cinder on the freeze-thaw properties of the improved soil. 

Results and Discussion The freeze-thaw deformation of silty sand can be inhibited by PCM. However, the volume change of paraffin-based PCM improved soil lacks stability with the increase of the freeze-thaw cycles. When the mass fraction of paraffin-based PCM is 8%, the volume change rate of the two improved soils is the smallest. Cinder can reduce the leakage of paraffin-based PCM, and the volume change rate of paraffin-based PCM decreases with the increase of the content of paraffin-based PCM. In contrast the adsorption effect of cinder on the paraffin-based PCM gradually decreases with the increase of freeze-thaw cycles. The unconfined compressive strength of all soils decreases with the increase of freeze-thaw cycles, of which the decline rate is first fast and then slow. The unconfined compressive strength of PCM-cinder improved soil is greater than that of PCM improved soil under the same cycle times. After 9 freeze-thaw cycles, the unconfined compressive strength of PCM modified soil with a PCM mass fraction of 10% is the lowest. The effect of temperature fluctuations on soil can be alleviated by the absorption or release of latent heat of the two improved soil, and the freezing or melting transitions within the soil can be delayed. The formation of the ice lens is delayed by the incorporation of cinder and PCM, and the particles of the improved soil are connected by the cementing material formed by PCM. This results in a dense and stable soil structure, significantly inhibiting the degree of expansion and contraction.

Conclusion The integration of paraffin-based PCM and cinder into silty sand effectively and stably manages freeze-thaw deformations in the soil. Hence, the freeze-thaw performance of soil is improved, contributing to a reduction in freezing damage to channel lining structure in seasonal frozen soil area. Simultaneously, the utilization rate of cinder is increased as well.

Keywords: paraffin-based phase change material; cinder; improved soil; silty sand; freeze-thaw property

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