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

这项研究解决了地球工程中一个引人注目的机会，将最近的发现应用于控制硅化生物中二氧化硅成核和生长的基本机制。仿生硅化（生物硅化）利用对这些生物发展的生化途径的见解来复制自然硅化过程和产品，以达到直接目的。这种方法为地面处理提供了许多优势：1)有可能采用一种新的、可持续的方法来制造胶结土，这种胶结土可以针对特定的地质力学性能问题进行定制；2)使用方便吗？可用、环保的化工材料；3)该过程不需要改变土壤和地下水的化学性质，在大多数天然土壤的pH值范围内进行；4)改变二氧化硅沉淀到土壤颗粒表面的能量屏障，也可能改善在间隙空间内形成的二氧化硅聚合物的性能。这种方法有一个明显的优点，它使生物体的生化机制发挥作用，而没有培养和维持活跃种群的困难。与传统的灌浆方法相比，生物硅化有可能节省地面改善项目的成本，因为所需的硅酸浓度可能会少得多。通过这种方法形成的水泥可能会产生更高的灌浆土强度和更好的长？与传统方法相比，项变形行为。基础实验室研究将建立在初步研究的基础上，利用生物硅化技术创建胶结砂标本。材料将包括渥太华20/30砂，市售硅酸盐溶液和胺？基于，聚电解质大分子。硅酸盐和大分子溶液的组成、浓度和输送方法会有所不同。非破坏性的原位微观结构表征和水泥在试样中的分布将使用x射线断层扫描。无侧限压缩和排水三轴压缩试验将用于评估随时间的强度增益；应力-应变、刚度和强度特性；并且，长期，恒定载荷强度。我们将对骨水泥断裂的仿生愈合潜力进行评估。将进行硅化实验，以确定水泥强度和水泥对颗粒粘结的强度。水泥的维氏硬度和弹性模量将由纳米？压痕测试。将与传统的硅酸盐？灌浆砂样。通过pi的地球工程和生物地球化学专业知识的独特结合，该项目是一个创新的机会，可能是变革性的进步，具有广泛的社会，经济和教育影响。社会效益来源于地面改善方法，该方法可以降低基础设施的成本，使用非？对人类和生态系统有毒，并防止工人接触化学品危害。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。我们将鼓励本科生参与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发展应用生物地球化学领域的专业知识。因此，他们将拥有将快速发展的科学发现从实验台上转化为地球工程规模的一线经验。与工程多样性增强中心合作，将招募学术上合格的女性、少数民族和第一代大学生。女学生将特别受益于共同主任P.Dove的指导，以及通过国家科学基金会赞助的advance evt项目提供的奖学金机会。

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.