Microbially-Induced Cementation of Sands by Denitrification

研究小组将调查反硝化细菌(反硝化)氧化有机化合物的使用。在砂岩中诱导碳酸盐胶结作用。微生物诱导碳酸盐沉淀(MICP)为各种重要的基础设施开发和地质灾害缓解问题提供了一种可持续、无中断和高能效的工程解决方案，包括修复液化潜力、提高地基承载能力、减少(甚至消除)开挖和隧道支撑要求。美国和国外的几个研究小组正在研究通过尿素溶解的MICP。然而，作为一种MICP法，反硝化有可能优于尿素分解法，因为反硝化细菌在地下无处不在，而且该工艺在厌氧条件下工作，例如在地下水位以下，而尿素分解需要氧气。反硝化细菌和营养物质将被引入实验室土柱中，孔隙水中含有碳酸钙溶液。碳酸盐沉淀将通过质量平衡测量孔隙流体中的钙浓度来监测，胶结的发展将通过土柱中的剪切波速测量来监测。这些柱试验将用于提炼反硝化作用的生物地球化学模型，建立反硝化作用的最佳营养物质组合，并建立反硝化作用下MICP的降水和胶结速率。对柱试验得到的试件进行三轴和简单剪切试验，以评估MICP量与试件的强度、刚度和液化势变化之间的关系。拟议的研究具有改变岩土工程实践的潜力，不仅通过开发一种新的、可持续的方法来改善地基，而且通过推进新兴的生物岩土工程领域。这项工作是在国家科学基金会探索性研究小额赠款(SGER)下启动的工作的继续。

The research team will investigate the use of oxidation of organic compounds by denitrifying bacteria (?denitrification?) to induce carbonate cementation in sand. Microbially induced carbonate precipitation (MICP) offers the promise of a sustainable, non-disruptive and energy efficient engineering solution to a variety of important infrastructure development and geologic hazard mitigation problems, including remediation of liquefaction potential, improving foundation bearing capacity, and reducing (or even eliminating) excavation and tunnel support requirements. MICP through ureolysis is being investigated by several research groups in the U.S. and abroad. However, denitrification is potentially superior to ureolysis as a MICP process in that denitrifying bacteria are ubiquitous in the subsurface and the process works under anaerobic conditions, e.g. below the water table, while ureolysis requires oxygenation. Denitrifying bacteria and nutrients will be introduced into a laboratory soil column with pore water containing calcium carbonate in solution. Carbonate precipitation will be monitored by mass balance measurement of calcium concentrations in the pore fluid and the development of cementation will be monitored by shear wave velocity measurements in the soil column. These column experiments will be used to refine a biogeochemical model for denitrification, establish an optimal nutrient mix for denitrification, and establish precipitation and cementation rates for MICP by denitrification. Triaxial and simple shear tests on specimens from the column experiments will be used to evaluate the relationship between the amount of MICP and changes in the strength, stiffness, and liquefaction potential of the specimens. The proposed research has the potential to transform geotechnical practice, not only by development of a new, sustainable approach to ground improvement but also by advancing the emerging field of biogeotechnical engineering. This work is a continuation of work initiated under a National Science Foundation Small Grant for Exploratory Research (SGER).