RAPID: Biostimulation for Biocementation at Field Scale Treatment Depths

当支撑结构基础的土壤，或用于堤防的土壤，以及其他土方工程缺乏足够的强度和刚度，无法令人满意地发挥作用时，通常需要土壤改良。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善土壤，尽管环境问题涉及高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的土壤改良替代方案，可以通过在土壤颗粒接触处沉淀方解石（生物胶结）来改善土壤的工程特性。尽管研究人员已经广泛证明了MICP改善土壤的能力，但由于需要培养和注射专门的非本地细菌菌株，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天然细菌在与实际工程应用相关的深度完成该过程的可行性，支持对该技术进步至关重要的研究。通过放弃将非本地细菌引入本地土壤生态系统，刺激本地细菌将消除种植成本和潜在的长期环境和生态影响。这一进展将为工业界提供财政和环境方面的奖励，促使它们将该方法付诸实践，从而获得重要的社会和环境效益。这项研究将涉及微生物学、岩土工程和地质学的跨学科专业知识，通过国际研究人员的合作。在减轻诸如液化等岩土工程危害通常需要的深度刺激原生细菌的可行性尚不清楚。本研究将对刺激天然土壤沉积物中原生细菌以完成深度生物胶结的分布、相对丰度和可行性提供重要的和前所未有的见解。以前的实验已经成功地证明了受刺激的原生细菌使生物胶结的能力，但这些研究只涉及表层土壤。然而，由于土壤有机质总量和氧气有效性的减少，原生土壤微生物的总浓度预计会随着深度的增加而降低。在这项研究中，将进行钻探和采样计划，以在自然土壤沉积物中从15米深的离散深度获取样品，用于微生物表征和岩土测试。将对获得的样品进行批量实验，利用微生物分析和过程生物地球化学的定时测量来优化增产处理。通过微生物学、生物地球化学和岩土监测，还将进行柱式实验，以评估增产技术的有效性，以丰富原生细菌种群，并改善深度土壤岩土特性。

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.