RAPID: Biostimulation for Biocementation at Field Scale Treatment Depths

当支撑建筑物基础的土壤或用于路堤的土壤，以及其他土方工程缺乏足够的强度和刚度时，通常需要进行土壤改良。目前的工程实践主要依赖于使用化学灌浆和机械方法来改良土壤，尽管环境问题涉及高隐含能量和有记录的地下水污染事件。微生物诱导方解石沉淀(MICP)提供了一种具有环保意识的生物介导型土壤改良替代方案，它可以通过方解石在土壤颗粒接触处的沉淀(生物固化)来改善土壤的工程性质。尽管研究人员已经广泛展示了MICP改良土壤的能力，但对专门的非本地细菌菌株的培养和注射的需要限制了该技术成为一种具有成本竞争力和环境允许的土壤改良技术。该奖项通过评估使用本地细菌在与实际工程应用相关的深度完成过程的可行性，支持对技术进步至关重要的研究。对本土细菌的刺激将通过放弃将非本土细菌引入本土土壤生态系统来消除培养成本以及潜在的长期环境和生态影响。这一进展将为工业采用该方法提供财政和环境激励，从而获得重要的社会和环境效益。这项研究将通过参与国际研究人员合作，涉及微生物学、岩土工程和地质学方面的跨学科专业知识。在减少液化等岩土灾害所需的深度刺激本地细菌的可行性尚不清楚。这项研究将对激发自然土壤沉积物中的本地细菌完成随深度的生物埋藏的分布、相对丰度和可行性提供重要和前所未有的见解。以前的实验已经成功地证明了受刺激的本地细菌能够进行生物固化，但这些研究只涉及表面土壤。然而，由于土壤有机质总量和氧气有效性的减少，本地土壤微生物的总浓度预计会随着深度的增加而下降。在这项研究中，将进行钻探和采样计划，从天然土壤沉积物中的离散深度达15米处获取样本，用于微生物特征和岩土测试。将对获得的样品进行批量实验，以使用微生物分析和过程生物地球化学的定时测量来优化刺激治疗。还将进行柱状试验，以评估通过微生物、生物地球化学和岩土监测来丰富本地细菌种群并随深度改善土壤岩土性质的刺激技术的有效性。

Soil improvement is often required when the soil supporting the foundations for structures, or soil used for embankments, and other earthworks lack sufficient strength and stiffness to perform satisfactorily. Current engineering practice relies primarily on the use of chemical grouts and mechanical methods to improve soils, despite environmental concerns regarding high embodied energies and documented groundwater contamination incidents. Microbially Induced Calcite Precipitation (MICP) offers an environmentally conscious bio-mediated soil improvement alternative that can improve a soil's engineering properties through the precipitation of calcite at soil particle contacts (biocementation). Although researchers have extensively demonstrated the ability of MICP to improve soils, the need for cultivation and injection of specialized non-native bacterial strains has restricted the technology from becoming a cost-competitive and environmentally permissible soil improvement technique. This award supports research critical to the advancement of the technology, by assessing the feasibility of using native bacteria to complete the process at depths relevant to practical engineering application. Stimulation of native bacteria will eliminate cultivation costs and potential long-term environmental and ecological impacts by forgoing the introduction of non-native bacteria into native soil ecosystems. This advancement would provide industry with financial and environmental incentives for adoption of the method into practice and therefore attain important societal and environmental benefits. This research will involve interdisciplinary expertise in microbiology, geotechnical engineering, and geology by engaging an international collaboration of researchers. The feasibility of stimulating native bacteria at depths typically required for mitigation of geotechnical hazards such as liquefaction is unknown. This research will provide important and unprecedented insight about the distributions, relative abundances, and feasibility of stimulating native bacteria in natural soil deposits to complete biocementation with depth. Previous experiments have successfully demonstrated the ability of stimulated native bacteria to enable biocementation, but these studies have only involved surficial soils. Total concentrations of native soil microorganisms are expected to decrease with depth however, due to reductions in total soil organic matter and oxygen availability. In this study, a drilling and sampling program will be conducted to obtain samples from discrete depths up to 15 meters within a natural soil deposit for microbiological characterization and geotechnical testing. Batch experiments will be performed on obtained samples to optimize stimulation treatments using microbiological analyses and timed measurements of process biogeochemistry. Column experiments will be also performed to evaluate the effectiveness of stimulation techniques to enrich for native bacterial populations and improve soil geotechnical properties with depth through microbiological, biogeochemical, and geotechnical monitoring.