School of Engineering and Technology, China University of Geosciences, Beijing, 100083, People's Republic of China.
Key Laboratory of Deep Geodrilling Technology, Ministry of Land and Resources, Beijing, 100083, People's Republic of China.
Environ Sci Pollut Res Int. 2023 Jul;30(32):78469-78481. doi: 10.1007/s11356-023-27862-w. Epub 2023 Jun 3.
Microbial-induced calcium carbonate precipitation (MICP) treatment of consolidated loess has the advantages of high efficiency and environmental protection. In this study, changes in the microscopic pore structure of loess before and after MICP treatment were compared and quantified, combined with test results at different scales, to better understand the mechanisms of MICP-consolidated loess. The unconfined compressive strength (UCS) of MICP-consolidated loess is significantly increased, and the stress-strain curve indicates improved strength and stability of the loess. X-ray diffraction (XRD) test results show that the signal strength of calcium carbonate crystals is significantly enhanced after loess consolidation. The microstructure of the loess was determined by scanning electron microscopy (SEM). The loess SEM microstructure images are quantitatively analyzed using comprehensive image processing methods (including gamma adjustment, grayscale threshold selection, median processing). The changes in microscopic pore area and average pore sizes (Feret diameter) of the loess before and after consolidation are described. More than 95% of the pores consist of pores with a pore area of less than 100 μm and an average pore size of less than 20 μm. The total percentage of pore numbers with pore areas of 100-200 and 200-1000 μm decreased by 1.15% after MICP consolidation, while those with 0-1 and 1-100 μm increased. The percentage of pore numbers with an average pore size greater than 20 μm decreased by 0.93%, while the 0-1, 1-10, and 10-20 μm increased. Particle size distributions revealed a significant increase in particle size after MICP consolidation, with an increase of 89 μm in D.
微生物诱导碳酸钙沉淀（MICP）处理固结黄土具有高效和环保的优点。本研究对比并量化了 MICP 处理前后黄土微观孔隙结构的变化，结合不同尺度的试验结果，更好地理解了 MICP 固结黄土的机理。MICP 固结黄土的无侧限抗压强度（UCS）显著提高，应力-应变曲线表明黄土的强度和稳定性得到改善。X 射线衍射（XRD）试验结果表明，黄土固结后碳酸钙晶体的信号强度显著增强。通过扫描电子显微镜（SEM）确定了黄土的微观结构。采用综合图像处理方法（包括伽马调整、灰度阈值选择、中值处理）对黄土 SEM 微观结构图像进行定量分析。描述了黄土固结前后微观孔隙面积和平均孔径（Feret 直径）的变化。超过 95%的孔隙由孔径小于 100 μm且平均孔径小于 20 μm的孔隙组成。MICP 固结后，孔径为 100-200 μm 和 200-1000 μm 的孔隙数量百分比减少了 1.15%，而孔径为 0-1 μm 和 1-100 μm 的孔隙数量百分比增加。平均孔径大于 20 μm 的孔隙数量百分比减少了 0.93%，而孔径为 0-1 μm、1-10 μm 和 10-20 μm 的孔隙数量百分比增加。粒径分布表明 MICP 固结后粒径显著增加，D 值增加了 89 μm。
