通过浸没通过微生物诱导的钙化物沉淀（MICP）改善沙土
Summary
这里介绍了微生物诱导的方解石沉淀（MICP）技术，通过浸泡改善土壤性能。
Abstract
本文旨在开发一种浸入法，以改善微生物诱导方解石沉淀（MICP）处理样品。组装了一批反应器，将土壤样品浸入水泥介质中。凝固介质可以自由扩散到批次反应器中的土壤样品中，而不是注入水泥介质。使用全接触柔性模具、刚性全接触模具和芯砖模具来制备不同的土壤样品支架。选择合成纤维和天然纤维来强化MICP处理的土壤样品。测量了MICP处理样品不同区域的沉淀CaCO3。CaCO3分布结果表明，沉淀的CaCO3采用浸入法在土壤样品中均匀分布。
Introduction
微生物诱导方解石沉淀（MICP）作为一种生物地面改良技术，能够提高土壤的工程性能。它用于增强土壤的强度、刚度和渗透性。MICP技术在土壤改良方面得到了全世界1、2、3、4的高度重视。碳酸盐降水自然发生，并且可能由土壤环境原生的非致病生物诱发。MICP生物地球化学反应是由尿素细菌、尿素和富含钙的溶液5、6的驱动。孢子菌糊化是一种高度活跃的尿酶，能催化方解石7、8的沉淀反应网络。尿素水解工艺产生溶解铵（NH4+）和无机碳酸盐（CO32-）。碳酸盐离子与钙离子发生反应，作为碳酸钙晶体沉淀。尿素水解反应如下所示：
沉淀的CaCO3可以将沙粒粘合在一起，提高MICP处理土壤的工程性能。MICP技术已应用于各种应用，如提高土壤的强度和刚度，修复混凝土，以及环境修复9，10，11，12，13,14,15.
赵等人16日研制出一种浸没方法制备MICP处理的样品。该方法采用土工纺织品制成的全接触柔性模具。沉淀的CaCO3均匀地分布在其MICP处理的样品中。Bu等人17开发出一种刚性全接触模具，通过浸入法制备MICP处理的光束样品。使用刚性全接触模具制备的 MICP 处理样品可形成合适的梁形。将MICP处理的样品分为4个，并测量CaCO3含量。按重量计，CaCO3含量从 8.4 ± 1.5% 到 9.4 ± 1.2% 不等，这表明 CaCO3通过浸没方法均匀分布于 MICP 处理的样品中。这些MICP处理样品也实现了更好的机械性能。这些MICP处理的生物标本达到950 kPa的弯曲强度，类似于20-25%的水泥处理样品（600-1300 kPa）。Li等人10将随机分布的离散纤维加入沙土中，采用MICP浸入法对土壤进行处理。他们发现，通过添加适当的纤维，可明显增强MICP处理土壤的剪切强度、延展性和失效应变。
MICP的浸入法已经不断改进10，16，17。该方法可用于制备 MICP 处理的土壤样品和 MICP 处理的预制建筑材料，如砖块和横梁。开发了样品制备模具的不同几何尺寸。在MICP处理的样品中加入纤维，以提高其性能。此详细协议旨在记录 MICP 治疗的浸入式方法。
Protocol
Representative Results
Discussion
本文提出了浸没的MICP技术。土壤样品被浸入批次反应器中，在MICP过程中被凝固介质完全渗透。在该方法中，应用全接触柔性模具、刚性全接触模具和芯砖模具制备MICP处理样品。
可针对不同的几何形状设计不同的模具。土工布纤维结构增加了沙与固结介质的接触面积，有效地增加了固结介质对土壤样品的渗透。大量的土工毛孔还使模具内部发生更多的降水，以提高MICP处理样?…
Declarações
The authors have nothing to disclose.
Acknowledgements
这项工作得到了国家科学基金会第1531382号赠款和MarTREC的支持。
Materials
| Ammonium Chloride, >99% | Bio-world | 40100196-3 (705033) | |
| Ammonium Sulfate | Bio-world | 30635330-3 | |
| Calcium Chloride Dihydrate, >99% | Bio-world | 40300016-3 (705111) | |
| Nutrient Broth | Bio-world | 30620056-3 | |
| Sodium Bicarbonate, >99% | Bio-world | 41900068-3 (705727) | |
| Sporosarcina pasteurii | American Type Culture Collection | ATCC 11859 | |
| Synthetic fiber | FIBERMESH | Fibermesh 150e3 | |
| Tris-Base, Biotechnology Grade, >99.7% | Bio-world | 42020309-2 (730205) | |
| Urea, USP Grade, >99% | Bio-world | 42100008-2 (705986) | |
| Yeast Extract | Bio-world | 30620096-3 (760095) |
Referências
- Cheng, L., Shahin, M. A., Mujah, D. Influence of key environmental conditions on microbially induced cementation for soil stabilization. Journal of Geotechnical and Geoenvironmental Engineering. 143 (1), 04016083-04016091 (2016).
- Whiffin, V. S., van Paassen, L. A., Harkes, M. P. Microbial carbonate precipitation as a soil improvement technique. Geomicrobiology Journal. 24 (5), 417-423 (2007).
- van Paassen, L. A., Ghose, R., van der Linden, T. J., van der Star, W. R., van Loosdrecht, M. C. Quantifying biomediated ground improvement by ureolysis: large-scale biogrout experiment. Journal of Geotechnical And Geoenvironmental Engineering. 136 (12), 1721-1728 (2010).
- Montoya, B. M., DeJong, J. T. Stress-strain behavior of sands cemented by microbially induced calcite precipitation. Journal of Geotechnical and Geoenvironmental Engineering. 141 (6), 04015019 (2015).
- DeJong, J. T., Fritzges, M. B., Nüsslein, K. Microbially induced cementation to control sand response to undrained shear. Journal of Geotechnical and Geoenvironmental Engineering. 132 (11), 1381-1392 (2006).
- Zhao, Q., et al. Factors affecting improvement of engineering properties of MICP-treated soil catalyzed by bacteria and urease. Journal of Materials in Civil Engineering. 26 (12), 04014094 (2014).
- Castanier, S., Le Métayer-Levrel, G., Perthuisot, J. P. Ca-carbonates precipitation and limestone genesis—the microbiogeologist point of view. Sedimentary Geology. 126 (1-4), 9-23 (1999).
- Burne, R. A., Chen, Y. Y. M. Bacterial ureases in infectious diseases. Microbes and Infection. 2 (5), 533-542 (2000).
- Bernardi, D., DeJong, J. T., Montoya, B. M., Martinez, B. C. Bio-bricks: biologically cemented sandstone bricks. Construction and Building Materials. 55, 462-469 (2014).
- Li, M., et al. Influence of fiber addition on mechanical properties of MICP-treated sand. Journal of Materials in Civil Engineering. 28 (4), 04015166 (2015).
- Achal, V., Kawasaki, S. Biogrout: a novel binding material for soil improvement and concrete repair. Frontiers in Microbiology. 7, 314 (2016).
- Al Qabany, A., Soga, K., Santamarina, C. Factors affecting efficiency of microbially induced calcite precipitation. Journal of Geotechnical and Geoenvironmental Engineering. 138 (8), 992-1001 (2011).
- Lin, H., Suleiman, M. T., Brown, D. G., Kavazanjian, E. Mechanical behavior of sands treated by microbially induced carbonate precipitation. Journal of Geotechnical and Geoenvironmental Engineering. 142 (2), 04015066 (2015).
- Lauchnor, E. G., Topp, D. M., Parker, A. E., Gerlach, R. Whole cell kinetics of ureolysis by sporosarcina pasteurii. Journal of Applied Microbiology. 118 (6), 1321-1332 (2015).
- Nafisi, A., Montoya, B. M. A new framework for identifying cementation level of MICP-treated sands. IFCEE. , (2018).
- Zhao, Q., Li, L., Li, C., Zhang, H., Amini, F. A full contact flexible mold for preparing samples based on microbial-induced calcite precipitation technology. Geotechnical Testing Journal. 37 (5), 917-921 (2014).
- Bu, C., et al. Development of a Rigid Full-Contact Mold for Preparing Biobeams through Microbial-Induced Calcite Precipitation. Geotechnical Testing Journal. 42 (3), 656-669 (2018).
- Li, M., Wen, K., Li, Y., Zhu, L. Impact of oxygen availability on microbially induced calcite precipitation (MICP) treatment. Geomicrobiology Journal. 35 (1), 15-22 (2018).
- Martinez, B. C., et al. Experimental optimization of microbial-induced carbonate precipitation for soil improvement. Journal of Geotechnical and Geoenvironmental Engineering. 139 (4), 587-598 (2013).
