Compositions of the culture medium.

Microbially induced calcium carbonate precipitation (MICP) is an environmentally friendly technology that improves soil permeability resistance through biocementation. In this study, 2D microscopic analysis and 3D volume reconstruction were performed on river sand after 24 cycles of bio-treatment based on stacked images and computed tomography (CT) scanning data, respectively, to extract biocementation patterns between particles. Based on the mutual validation findings of the two techniques, three patterns in the biocemented sand were identified as G-C-G, G-C, and G-G. Specifically, 2D microscopic analysis showed that G-C-G featured multi-particle encapsulation and bridging, with a pore filling ratio of 81.2%; G-C was characterized by locally coated particle layers, with a pore filling ratio of 19.7%; and the G-G was marked by sporadic filling of interparticle pores, with a pore filling ratio of 11.7%. G-C-G had the best cementation effect and permeability resistance (effective sealing rate of 68.5%), whereas G-C (effective sealing rate of 2.4%) had a relatively minor contribution to pore-filling and flow sealing. 3D volume reconstruction showed that G-C-G had the highest pore filling rate, followed by G-G and G-C. The average filling ratios of area and volume for G-C-G were 83.979% and 77.257%, respectively; for G-G 20.360% and 23.600%; and for G-C 11.545% and 11.250%. The analysis of the representative element volume (REV) was conducted, and the feasibility and reliability of the micro-scale pattern extraction results were confirmed to guide the analysis of macro-scale characteristics. The exploration of the effectiveness of cementation patterns in fluid sealing provides valuable insights into effective biocementation at the pore scale of porous media, which may inspire future research.

微生物诱导碳酸钙沉淀（Microbially induced calcium carbonate precipitation, MICP）是一种通过生物胶结作用提升土体抗渗性能的环保技术。本研究基于堆叠显微图像与计算机断层扫描（computed tomography, CT）数据，分别对经过24轮生物处理后的河砂开展二维显微分析与三维体域重建，以提取颗粒间的生物胶结模式。基于两种技术的相互验证结果，本研究将胶结砂中的胶结模式划分为G-C-G、G-C与G-G三类。具体而言，二维显微分析结果显示，G-C-G模式表现为多颗粒包裹与桥接结构，孔隙填充率达81.2%；G-C模式以局部包覆颗粒层为特征，孔隙填充率为19.7%；G-G模式则表现为颗粒间孔隙的零星填充，孔隙填充率为11.7%。G-C-G模式的胶结效果与抗渗性能最优，有效封堵率达68.5%，而G-C模式对孔隙填充与流体封堵的贡献相对有限，其有效封堵率仅为2.4%。三维体域重建结果表明，G-C-G模式的孔隙填充率最高，其次为G-G与G-C模式。其中，G-C-G模式的面积与体积平均填充率分别为83.979%与77.257%；G-G模式分别为20.360%与23.600%；G-C模式分别为11.545%与11.250%。本研究还开展了代表性体积单元（representative element volume, REV）分析，证实了微观尺度胶结模式提取结果的可行性与可靠性，可为宏观尺度特性分析提供指导。对胶结模式流体封堵有效性的探索，可为多孔介质孔隙尺度下的高效生物胶结研究提供宝贵见解，有望为后续相关研究提供新思路。