Applying Insights from Biosilicification Processes to Ground Treatment: A Bio-Inspired Approach for Geoengineering

这项研究解决了一个令人信服的机会，在地球工程应用最新发现的基本机制控制硅化生物体中的硅成核和生长。 仿生硅化（biosilicification）利用这些生物体开发的生物化学途径的见解，复制，为有针对性的目的，天然硅化过程和产品。 这种方法为地基处理提供了许多优点：1）可能是一种新的、可持续的方法，可以根据具体的地质力学性能问题来制造水泥土; 2）使用方便？可用的、环境友好的化学材料; 3）不需要改变土壤和地下水的化学性质，并且该过程在大多数天然土壤的pH范围内进行;以及4）改变二氧化硅沉淀到土壤颗粒表面上的能量屏障，并且还可以改善在间隙空间内形成的二氧化硅聚合物的性质。 这种方法的显著优点是，使生物体的生化机制发挥作用，而不存在培养和维持活跃种群的困难。 与传统的灌浆方法相比，生物硅化具有节省地基改良项目成本的潜力，因为所需的磷酸浓度可能要低得多。与传统方法相比，基础实验室研究将建立在初步研究的基础上，利用生物硅化作用制作胶结砂标本。 材料将包括渥太华20/30砂，市售硅酸盐溶液和胺？基于，非线性大分子。 硅酸盐和高分子溶液的组成、浓度和输送方法将有所不同。 将使用X射线断层扫描法对样本中水泥的原位微观结构和分布进行非破坏性表征。 无侧限压缩和排水三轴压缩试验将用于评估强度随时间的增加;应力-应变、刚度和强度特性;以及长期恒定荷载强度。 将评价骨水泥粘合断裂的仿生愈合潜力。 将进行硅化实验，以确定水泥强度和水泥与颗粒结合的强度。 水泥的维氏硬度和弹性模量将由纳米？压痕试验 将与传统硅酸盐进行比较？灌浆砂试样。通过地球工程和地球化学专业知识的独特组合，该项目是一个创新的机会，可能是变革性的，具有广泛的社会，经济和教育影响的进步。 社会效益来自地面改善方法，可以降低基础设施的成本，使用材料是非？对人类和生态系统有毒，并防止工人接触化学危害。 考虑到这种新工艺的商业应用潜力，对岩土工程专业的影响可能很大。 在项目期间与实践者的互动将是将发现转化为实践的特别富有成效的途径。 本科生将被鼓励从事这个令人兴奋的跨学科研究项目。 该项目的研究生将有机会在不断发展的应用地球化学领域发展专业知识。 因此，他们将拥有将快速发展的科学发现从实验室到地球工程规模的一线经验。 与工程多样性增强中心一起，将招募学术合格的妇女、少数民族和第一代大学生。 女学生将特别受益于共同PI P.Dove的指导，并通过NSF赞助的AdvanceVT计划获得奖学金机会。

This research addresses a compelling opportunity in geoengineering to apply recent discoveries in the fundamental mechanisms controlling silica nucleation and growth in silicifying organisms. Biomimetic silicification (biosilicification) uses insights into biochemical pathways developed by these organisms to replicate, for a directed purpose, natural silicifying processes and products. This approach confers a number of advantages for ground treatment: 1) Potential for a new, sustainable means of creating cemented soil that can be tailored to specific geomechanical performance problems; 2) Uses readily?available, environmentally benign chemical materials; 3) Changes to soil and groundwater chemistry are not required and the process proceeds within the pH range of most natural soils; and, 4) Modifies the energy barriers to silica precipitation onto soil grain surfaces and may also improve the properties of the silica polymer that forms within the interstitial space. This approach has the distinct advantage of putting to work the biochemical machinery of organisms without the difficulties of culturing and maintaining active populations. Biosilicification has the potential for cost savings on ground improvement projects over traditional grouting methods because concentrations of silicic acid required could be much less. Cements formed by this process can potentially yield higher grouted soil strength and better long?term deformation behavior compared to traditional methods. Basic laboratory research will build on insights from preliminary studies to create cemented sand specimens using biosilicification. Materials will consist of Ottawa 20/30 sand, commercially available silicate solutions and amine?based, polyelectrolyte macromolecules. Compositions, concentrations and delivery methods of silicate and macromolecule solutions will be varied. Nondestructive in-situ microstructure characterization and distribution of cement in specimens will be made using x-ray tomography. Unconfined compression and drained triaxial compression tests will be used to assess strength gain with time; stress-strain, stiffness and strength behavior; and, long-term, constant load strength. The potential for biomimetic healing of broken cement bonds will be evaluated. Silicification experiments will be conducted to determine cement strength and the strength of cement to grain bonds. Vickers hardness and elastic modulus of the cement will be determined by nano?indentation tests. Comparisons will be made with traditional silicate?grouted sand specimens. Through the unique combination of the geoengineering and biogeochemistry expertise of the PIs, this project is an opportunity for innovative, and possibly transformative, advances with broad societal, economic and educational impacts. Societal benefits are derived from a ground improvement method that could lower the cost of infrastructure, using materials that are non?toxic to humans and ecosystems, and prevent worker exposure to chemical hazards. Considering the potential for commercial application of this new process, impacts to the geotechnical profession are possibly large. Interactions with practitioners during the project will be an especially fruitful avenue for transferring the discoveries to practice. Undergraduate students will be encouraged to work on this exciting interdisciplinary research project. Graduate students on the project will have the opportunity to develop expertise in the growing area of applied biogeochemistry. As such, they will have frontline experience in transforming rapidly advancing scientific discoveries from the bench top to the geoengineering scale. In conjunction with the Center for Enhancement of Engineering Diversity, academically qualified women, minorities and first generation university students will be recruited. Women students will especially benefit from mentoring by co-PI P.Dove and from the scholarship opportunities available through the NSF sponsored AdvanceVT program.