Zhu Jin, Wei Renjie, Dai Di, Li Liangliang, Shang Zhiyang, Jiang Zhao, Peng Jie
School of Civil Engineering, Wanjiang University of Technology, Maanshan, China.
Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing, China.
PLoS One. 2025 Jul 9;20(7):e0327568. doi: 10.1371/journal.pone.0327568. eCollection 2025.
In recent years, the reinforcement of calcareous sands using the microbially induced calcium carbonate precipitation (MICP) method has emerged as a prominent research area. Nevertheless, a significant drawback of the MICP method is that multiple treatments with the cementing solution are required to achieve the desired improvement effect. To address this limitation, this study proposes an optimized MICP strategy through adding the ferric ion into cementing solutions. The effectiveness of the proposed method was investigated by analyzing the precipitation of CaCO3, unconfined compressive strength (UCS) and permeability coefficient through aqueous solution test and sand column reinforcement test. Experimental results revealed that ferric ion incorporation significantly altered CaCO3 crystal morphology and particle size distribution in aqueous solution test. In sand column tests, specimens treated with cementing solution with ferric ion achieved the UCS of 2.83 MPa after five injection cycles, representing a 15-fold increase compared to conventional MICP-treated specimens under the same test conditions. At the same time, permeability coefficients decreased by two orders of magnitude relative to untreated sand. The micro-structure analysis showed that ferric ions were involved in the reaction to generate a clogging precipitate, which changed the distribution of bio-CaCO3 in the pores of the soil, thereby improving the cementation efficiency. These findings indicate that the addition of ferric ion can overcome the shortcoming of frequent treatment of cementing solution in MICP-reinforced calcareous sand, and provide new insights for the development of effective biological grouting strategies.
近年来，利用微生物诱导碳酸钙沉淀（MICP）方法加固钙质砂已成为一个突出的研究领域。然而，MICP方法的一个显著缺点是需要用胶结溶液进行多次处理才能达到预期的改良效果。为解决这一局限性，本研究提出了一种通过向胶结溶液中添加铁离子来优化MICP的策略。通过水溶液试验和砂柱加固试验，分析碳酸钙沉淀、无侧限抗压强度（UCS）和渗透系数，研究了该方法的有效性。实验结果表明，在水溶液试验中，铁离子的加入显著改变了碳酸钙的晶体形态和粒径分布。在砂柱试验中，用含 铁离子的胶结溶液处理的试样在五个注入循环后达到了 2.83 MPa 的无侧限抗压强度，与相同试验条件下传统 MICP 处理的试样相比提高了 15 倍。同时，渗透系数相对于未处理的砂降低了两个数量级。微观结构分析表明，铁离子参与反应生成堵塞沉淀物，改变了生物碳酸钙在土壤孔隙中的分布，从而提高了胶结效率。这些研究结果表明，添加铁离子可以克服MICP加固钙质砂中胶结溶液频繁处理的缺点，并为开发有效的生物注浆策略提供新的见解。
