Microstructure damage characteristics and its mechanism of undisturbed loess suffering to weak acid leaching
Microstructure damage characteristics and its mechanism of undisturbed loess suffering to weak acid leaching
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DOI：
10.1007/s10064-023-03098-3
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发表时间：
2023-02
影响因子：
4.2
通讯作者：
Lei Zhang;Ruixin Yan;Jian-bing Peng;Yan-jun Shen;Jinyuan Zhang;Yu Zhang
中科院分区：
文献类型：
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作者：
Lei Zhang;Ruixin Yan;Jian-bing Peng;Yan-jun Shen;Jinyuan Zhang;Yu Zhang
中国西部黄土高原是典型的生态脆弱区。随着我国西部能源化工基地的建设，工业废水等弱酸性污水渗入黄土的情况日益增多。在这项研究中，原状黄土进行了室内淋滤试验，在不同的pH值（pH = 3，5，7），不同的时间（5，10，15天）。通过对比分析弱酸性溶液淋溶前后黄土的矿物组成、离子浓度和微观结构，探讨了弱酸性溶液淋溶对黄土结构的损伤特征。结果表明，浸水后可溶性胶结物矿物的溶解和不溶性胶结物的淋溶导致土粒结合强度降低。颗粒间的接触面积随着颗粒重排的发生而增大，由点接触变为面接触。在坍缩过程中，由于骨架颗粒的溶解、崩解、重排和旋转，粘结材料也会重新排列。一些亚稳聚集体和团聚体会由于酸溶解而分解。在溶蚀和侵蚀的耦合作用下，土体的细观结构面遭到破坏。微观结构颗粒随酸液进入优势渗流通道，在滞水层的大量堆积和冲刷下，在土体下部形成软化带，导致宏观结构面破坏，形成化学腐蚀地质灾害。
The Loess Plateau in western China is a typical fragile ecological area. With the construction of an energy and chemical industry base in western China, weak acid sewage such as industrial wastewater permeating into the loess is increasing. In this study, indoor leaching tests of undisturbed loess were conducted at different pH (pH = 3, 5, and 7) for different durations (5, 10, and 15 days). By comparing and analyzing the mineral compositions, ion concentrations of the filtrates, and microstructure of loess before and after leaching, the structural damage characteristics of loess under weak acid leaching were explored. The results show that the dissolution of soluble cement minerals and the leaching of insoluble cement after immersion lead to the decrease of soil particle bonding strength. The contact area between particles increases with the occurrence of particle rearrangement, changing from point contact to surface contact. The binding material will also rearrange due to the dissolution, disintegration, rearrangement, and rotation of skeleton particles during collapse. Some metastable aggregates and agglomerates will be decomposed due to acid dissolution. Under the coupling effect of dissolution and erosion, the micro-meso-structural plane of soil is destroyed. The microscopic structural particles enter the dominant seepage channel with the acid solution, and under the large accumulation and erosion of the stagnant water layer, a softening zone is formed in the lower part of the soil, resulting in the destruction of the macroscopic structural plane and the formation of chemical corrosion geological disasters.