Translating from Kangaroo Rat Burrows to Geotechnical Engineering by Uncovering Fundamental Processes

该奖项支持研究，以了解袋鼠鼠的微生物组在极端沙漠环境中构建弹性结构的作用，以及如何将这些知识扩展到极端环境中的人类岩土工程结构。袋鼠鼠在多年的时间里建造精心制作的洞穴，并在很长一段时间内占据它们。洞穴在沙漠中保持开放和稳定，并在恶劣的沙漠条件下生存，每天和每年极端的相对湿度和温度波动以及山洪暴发事件。这项研究测试了这样一种假设，即洞穴微生物组是由袋鼠的颊囊或脚中的微生物群落决定的，并且在这种微生物组中形成生物膜（即，洞穴生物膜）对于随机波动的沙漠环境中洞穴的稳定性至关重要。从这个项目中获得的基本认识可以转化为可持续的地面改良技术的设计，用于岩土工程实践，特别是在容易发生滑坡和基底坍塌的地方。该研究将在岩土工程和地质环境工程、生物工程和生物学领域的研究人员、研究生和本科生之间建立直接合作。 该研究将具体测试以下假设：（i）由于土壤和生物膜的水分保持，洞穴生物膜增强的沙漠土壤的吸力应力特征曲线是饱和度的非单调函数，并且无论湿度，饱和度和温度的极端波动如何，都有助于有效应力，维持洞穴的稳定性，以及（ii）生物膜降低洞穴顶部的水力传导性，从而防止洞穴在风暴期间被淹没。实验计划将包括在实验室中生长洞穴生物膜，并确定洞穴生物膜增强土壤在整个饱和度范围内以及经过多次湿/干和热/冷循环后的强度。该研究还将调查胶结剂如何保水（即，洞穴生物膜）在环境条件的极端波动下有助于吸力以维持洞穴稳定性。这对于建立干旱环境中桑迪稳定性的力学基础是重要的。此外，本研究还将研究洞穴生物膜的加入对沙漠沙导水率的影响。这项研究的结果将揭示最多产的生态系统工程师之一如何在沙漠中挖掘复杂，稳定和可持续的地下环境，以及个体的表型如何从微生物组延伸到洞穴选址，该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的评估来支持。影响审查标准。

This award supports research to understand the role of kangaroo rats' microbiome in constructing resilient structures in extreme desert environments and how this knowledge can be scaled up to human geotechnical structures in extreme environments. Kangaroo rats construct elaborate burrows over multiple years and occupy them for extended periods of time. The burrows remain open and stable in desert sand and survive the harsh desert conditions, with extreme daily and yearly relative humidity and temperature fluctuations and flash-flood events. This research tests the hypothesis that the burrow microbiome is determined by the microbial community in cheek pouches or feet of kangaroo rats and that biofilms formed in this microbiome (i.e., burrow biofilms) are crucial to burrow stability in stochastic, fluctuating desert environments. The fundamental understanding gained from this project could translate to the design of sustainable ground improvement techniques to be used in geotechnical engineering practice, particularly in locations prone to landslides and substrate collapse. The research will establish direct collaborations among researchers, graduate students, and undergraduate students in geotechnical and geoenvironmental engineering, bioengineering, and biology. The research will specifically test the hypotheses that (i) the suction stress characteristic curve of burrow-biofilm-enhanced desert soil is a non-monotonic function of saturation, due to water retention by both the soil and the biofilm, and contributes to effective stress regardless of the extreme fluctuations in humidity, saturation, and temperature, to maintain the stability of the burrows and (ii) biofilms reduce the hydraulic conductivity of burrow ceilings, and therefore prevent flooding of the burrows during storms. The experimental program will include growing the burrow biofilms in the laboratory and determining the strength of burrow-biofilm-enhanced soil over the entire range of saturation and after multiple wet/dry and heat/cool cycles. The research will also investigate how water retention by the cementing agent (i.e., burrow biofilm) contributes to suction stress to maintain burrow stability under extreme fluctuations in environmental conditions. This is important for establishing the mechanistic basis for stability in sandy soils in arid environments. In addition, the research will study how the hydraulic conductivity of desert sand changes with the addition of burrow biofilm. Results from this research will reveal how one of the most prolific ecosystem engineers digs complex, stable, and sustainable underground environments in desert sand and how an individual’s phenotype extends from their microbiome, to burrow site selection, and more broadly to landscape biogeomorphology.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.