| 陈小双,徐兴倩,刘剑,赵熹,尹亚敏,王海军,王能龙.镉污染红黏土强度劣化机理分析[J].农业环境科学学报,2024,43(7):1503-1511. |
| 镉污染红黏土强度劣化机理分析 |
| Strength degradation mechanism analysis of cadmium-contaminated laterite |
| 投稿时间：2024-01-03 |
| DOI：10.11654/jaes.2024-0008 |
| 中文关键词: 红黏土 镉污染 抗剪强度 微观结构 劣化效应 |
| 英文关键词: laterite cadmium contamination shear strength microstructure degradation effect |
| 基金项目:国家自然科学基金项目（42367025）；云南省基础研究计划面上基金项目（202101AT070271）；云南省农业联合专项（202301BD070001-171）；云南省高层次人才培养支持计划“青年拔尖人才”专项（YNWR-QNBJ-2020-030） |
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| 中文摘要: |
| 为探究镉污染条件下红黏土的微观结构演化对土体抗剪强度的影响，揭示镉污染红黏土的强度劣化机理，本研究通过直剪试验、X 射线衍射（XRD）分析和扫描电子显微镜（SEM）观察研究了镉污染红黏土的剪切特性和微观结构特征。结果表明：随着镉含量的增加，黏聚力平均减小 25.5%，内摩擦角平均增大 21.1%，抗剪强度出现劣化趋势，剪切破坏面形态凹凸越来越明显；微观影像显示出颗粒蚀化现象，孔隙发育平均增大 11.8%，且呈蜂窝状，土颗粒接触方式由角-面、边-面、面-面转为角-边、点-面接触，微观结构指标（颗粒丰度、定向频率及孔隙分形维数）反映出土颗粒由强联结转化为弱接触的变化特征；因黏土颗粒对镉离子吸附能力较强，导致扩散双电层被压缩，同时镉离子与黏土中碳酸盐类发生水解反应，从而降低了黏土颗粒间结合水膜连结力，黏聚结构功能逐渐弱化。研究表明，镉污染对红黏土抗剪强度产生劣化效应，在地表径流冲刷作用下易加剧耕地层水土流失等危害。 |
| 英文摘要: |
| In this study, we revealed the strength degradation mechanism of cadmium-contaminated laterite to investigate how cadmiumcontaminated laterite microstructure evolution influences the shear strength of the soil. We studied the shear and microstructure characteristics of cadmium-contaminated laterite using direct shear tests, X-ray diffraction（XRD） analysis, and scanning electron microscopy. Our results demonstrated the following：Cohesion decreased by 25.5% and the internal friction angle increased by 21.1% on average with the increasing cadmium content. Therefore, the shear strength tended to deteriorate, and the shear failure surface shapes became more evident. The microstructure of cadmium-contaminated laterite underwent significant restructuration with the particle erosion phenomenon, coupled with pore development and honeycomb formation based on the microscopic image analysis. Honeycombed pore development increased by 11.8% on average. The soil particle contact modes changed from the angle-side, edge-side, face-face to angleside, and point-face. The microstructure indices（particle abundance, orientation frequency, and pore fractal dimension）reflected the change soil particle characteristics from strong to weak contact. Due to the strong adsorption capacity of clay particles to cadmium ions, the diffusion electrical double layer was compressed and hydrolysis occurred between the cadmium ions and carbonates in the clay. Therefore, the binding force of the water film between the clay particles was reduced and the cohesive structural function gradually weakened. In summary, cadmium contamination exerts a deterioration effect on laterite shear strength to worsen soil erosion in the cultivated land layer under the surface runoff effect easily. |
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