Collaborative Research: Implementation Strategies and Performance of Unsaturated Bio-Cemented Dune Sand

这项研究将探索一种新的沙丘保护方法，利用生物胶结来加固和增强天然防护结构。在极端的海浪和风暴事件中，沙丘往往是建筑环境的第一道防线。为了保持有效性，面对这些事件，沙丘必须抵抗侵蚀。了解沙丘侵蚀的物理机制对于设计缓解沙丘侵蚀的方法至关重要。研究小组将在俄勒冈州立大学的大型波浪水槽(LWF)中探索多种处理实施技术，并在现场规模的极端条件下评估它们的性能。沙丘将在LWF中建造，在原地进行生物胶结，并经受一系列波浪淹没，以便观察和量化其性能。这项大规模的工作将由实验室和数值研究相结合来支持。数值调查将深入了解每种处理实施方案首选的负荷条件，以及处理设计(例如，所需的处理尺寸)对自然环境的影响最小，同时仍提供所需的工程性能。这项工作的结果将为用生物胶结增强沿海沙丘提供指导，以防止在极端事件中对基础设施的破坏。生物胶结可能是减轻沙丘侵蚀的可行方法，这反过来将在极端事件中保护沿海基础设施。我们将探索两种实现生物胶结的方法。第一种实施技术将在沙丘内部深处诱导生物胶结作用；这将导致未胶结的表层，这可能会侵蚀，但对沿海栖息地的影响也是最小的。第二种方法将用于快速部署，例如，为预计将袭击易受攻击的沙丘的预报风暴事件做准备。这种快速方法将被喷洒到沙丘上，而不是注入，因为这种快速应用更有可能在快速部署中实施。此外，还将探索两种诱导生物胶结的方法：微生物诱导碳酸盐沉淀(MICP法)和酶诱导碳酸盐沉淀(EICP法)。EICP的实施将由NSF生物中介和生物启发岩土工程研究中心(CBBG)进行。研究方法将包括在NHERI Hinsdale波浪研究实验室(HWRL)进行接近原型规模的实验；这是通过与美国国家科学基金会现有的项目--极端浪涌和波浪事件期间沙丘侵蚀物理--合作实现的，该项目包括在HWRL大波浪水槽(LWF)放置近1000吨沙子，这是北美最大的同类沙子，也是世界前10名。除了LWF的实验外，还计划进行一项补充的实验室测试和综合数值模拟程序，以评估实施策略与整体沙丘表现的效果。这项研究将通过提供良好控制和仪器化的案例研究来定量比较实施技术对沙丘性能的影响，从而推动生物胶结技术的发展。两种处理方法产生的胶结模式预计不同；然而，这两种处理方法的性能尚不清楚。这种方法不仅将开发两种不同处理实施的原型规模的案例研究，而且还将提供生物胶结沙丘在极端风暴载荷条件下的案例研究。数值模拟方法将提供一个框架来设计和评估极端波浪载荷下生物胶结的稳定性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This research will explore a novel approach for dune protection using bio-cementation to stabilize and enhance natural protective structures. Dunes often present the first line of defense for the built environment during extreme wave surge and storm events. In order to remain effective, dunes must resist erosion in the face of these incidents. Understanding the physics of dune erosion is critical for devising ways to mitigate it. The research team will explore multiple treatment implementation techniques and assess their performance under extreme conditions at field-scale in a large wave flume (LWF) at Oregon State University. Dunes will be constructed in the LWF, bio-cemented in-place, and subjected to a series of wave inundations so that their performance may be observed and quantified. The large-scale work will be supported by coupled laboratory and numerical investigations. The numerical investigation will provide insight into the loading conditions for which each treatment implementation alternative is preferred and the treatment design (e.g., required treatment dimensions) to have minimal impact on the natural environment while still providing the required engineering performance. The resulting outcome of this work will provide guidance for enhancing coastal dunes with bio-cementation to prevent damage to infrastructure during extreme events.Bio-cementation may be a viable method to mitigate dune erosion, which in turn would protect coastal infrastructure during extreme events. We will explore two approaches to implement bio-cementation. The first implementation technique will induce bio-cementation at depth within the dune; this will result in an uncemented surficial layer which may erode but will also minimally impact the coastal habitat. The second approach will be geared towards rapid deployment, for example, in preparation for a forecasted storm event anticipated to hit vulnerable dunes. This rapid approach will be sprayed onto the dunes, instead of injected, since this quick application is more likely to be implemented in a rapid deployment. Furthermore, two methods to induce bio-cementation will be explored: microbial induced carbonate precipitation (MICP) and enzyme induced carbonate precipitation (EICP). The EICP implementation will be conducted by the NSF Engineering Research Center for Bio-mediated and Bio-inspired Geotechnics (CBBG). The research approach will include near prototype-scale experiments in the NHERI Hinsdale Wave Research Laboratory (HWRL); this is made possible by collaborating with an existing NSF project, Physics of Dune Erosion During Extreme Surge and Wave Events, which includes placing nearly 1000 tons of sand in the HWRL Large Wave Flume (LWF), the largest of its type in North America and in the top 10 in the world. In addition to the experiments in the LWF, a complementary laboratory testing and integrated numerical modeling program are planned to assess the effects of implementation strategies with overall dune performance. This research will advance bio-cementation technology by providing well-controlled and instrumented case studies to quantitatively compare the effect of implementation techniques on the performance of dunes. The resulting cementation patterns from the two treatment approaches are expected to be different; however, the performance of the two treatment approaches is unknown. This approach will not only develop prototype-scale case studies of two different treatment implementations, but also provide case studies of bio-cemented sand dunes subjected to extreme storm loading conditions. The numerical simulation approach will provide a framework to design and evaluate the stability of the bio-cementation under extreme wave loading.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.