Lai Yongming, Liu Shiyu, Cai Yanyan, Yu Jin
College of Civil Engineering, Huaqiao University, Xiamen 361021, China.
College of Resource Engineering, Longyan University, Longyan 364000, China.
Materials (Basel). 2023 Sep 14;16(18):6211. doi: 10.3390/ma16186211.
Different sands have significant influences on MICP reinforcement effects. Using calcium carbonate production and bioflocculation lag period as evaluation criteria, this study investigates the optimal theoretical pH values of bacterial solutions with different concentrations. We reinforced four different sands using MICP at the optimal theoretical pH, and based on permeability, moisture retention, raindrop erosion, wind erosion, penetration, and SEM tests, the influence of sand properties on low-pH MICP reinforcement was analyzed and the low-pH MICP mechanism was revealed. The results indicate the following: (1) The optimal theoretical pH values for bacterial solutions with concentrations of 0.67 × 10 cells/mL, 3 × 10 cells/mL, and 10 × 10 cells/mL are 4.5, 3, and 4, respectively. (2) With 0.67 × 10, 3 × 10, and 10 × 10 cells/mL bacterial solutions, the strength of tailings sand containing calcium salt was 21.15%, 44.42%, and 13.61% higher than that of quartz sand, respectively. The effective reinforcement depth of alkaline reclaimed sand was 10, 8, and 6 mm lower than that of neutral calcareous sand, respectively. The strength of fine tailings sand was 70.41%, 58.04%, and 22.6% higher than that of coarse reclaimed sand. The effective reinforcement depth of fine quartz sand was 6, 4, and 4 mm lower than that of coarse calcareous sand. (3) Low pH temporarily suppresses urease activity, delaying calcium carbonate flocculation and enhancing reinforcement uniformity. To achieve optimal reinforcement effects, adjusting the actual optimal pH values of bacterial solution based on sand properties is essential in engineering applications.
不同的沙子对微生物诱导碳酸钙沉淀（MICP）加固效果有显著影响。本研究以碳酸钙生成量和生物絮凝延迟期为评价标准，探究不同浓度菌液的最佳理论pH值。在最佳理论pH值下，我们用MICP对四种不同的沙子进行加固，并基于渗透性、保水性、雨滴侵蚀、风蚀、贯入度和扫描电子显微镜（SEM）测试，分析了沙子性质对低pH值MICP加固的影响，揭示了低pH值MICP的作用机制。结果表明：（1）浓度为0.67×10⁶个细胞/毫升、3×10⁶个细胞/毫升和10×10⁶个细胞/毫升的菌液，其最佳理论pH值分别为4.5、3和4。（2）对于浓度为0.67×10⁶、3×10⁶和10×10⁶个细胞/毫升的菌液，含钙盐尾矿砂的强度分别比石英砂高21.15%、44.42%和13.61%。碱性再生砂的有效加固深度分别比中性钙质砂低10毫米、8毫米和6毫米。细尾矿砂的强度分别比粗再生砂高70.41%、58.04%和22.6%。细石英砂的有效加固深度分别比粗钙质砂低6毫米、4毫米和4毫米。（3）低pH值会暂时抑制脲酶活性，延缓碳酸钙絮凝并增强加固均匀性。在工程应用中，根据沙子性质调整菌液的实际最佳pH值对于实现最佳加固效果至关重要。
