In the ground improvement field, microbially induced carbonate precipitation (MICP) is a novel bio-based soil improvement technique. To apply this technique, the presence of an actual construction site is needed to clearly understand the strength of increment and permeability reduction mechanisms with the specific trend of bacterial species. In this study, constant head permeability tests were performed on the three species of urease-producing bacteria, which were isolated from land and sea (estuary and deep-seabed). Permeability control and strength increment effect were evaluated with the constant head permeability and cone penetration tests. In all the test cases, the hydraulic conductivity decreased with the increment of the number of cementation solution injections and finally reached to almost two orders decreased. Moreover, the difference in the bacterial species showed a different permeability trend of the hydraulic conductivity despite the same amount of biomineral being deposited. Thus, the type of bacterial species has different chemical deposit mechanisms. In contrast, strength enhancement is affected by the deposited biomineral volumes from the cementation solution with bacterial specific urease enzyme. Consequently, the application of MICP needs to select the appropriate bacterial species for each type of ground improvement.

中文翻译：

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产生脲酶的细菌对砂土渗透性和强度控制的影响

在地面改良领域，微生物诱导的碳酸盐沉淀（MICP）是一种新型的基于生物的土壤改良技术。要应用此技术，需要存在一个实际的施工现场，以清楚地了解细菌种类的特定趋势所带来的增加强度和渗透率降低机制。在这项研究中，对从陆地和海洋（河口和深海底）分离出的三种产生脲酶的细菌进行了恒定的头部通透性测试。渗透率控制和强度增加效果通过恒定的水头渗透率和锥孔渗透测试进行评估。在所有测试案例中，水力传导率均随着胶结溶液注入次数的增加而降低，并最终下降至几乎两个数量级。而且，尽管沉积了相同数量的生物矿物质，细菌种类的差异显示了水力传导性的不同渗透趋势。因此，细菌种类的类型具有不同的化学沉积机理。相反，强度增强受具有细菌特异性脲酶的胶结溶液中沉积的生物矿物质量的影响。因此，MICP的应用需要为每种地面改良类型选择合适的细菌种类。强度的提高受具有细菌特异性脲酶的胶结溶液中沉积的生物矿物质量的影响。因此，MICP的应用需要为每种地面改良类型选择合适的细菌种类。强度的提高受具有细菌特异性脲酶的胶结溶液中沉积的生物矿物质量的影响。因此，MICP的应用需要为每种地面改良类型选择合适的细菌种类。