SGER: Air Entrapment for Liquefaction Mitigation

0234365, Mishac Yegian，东北大学“空气夹持缓解液化”这一行动是为了支持一项减缓土壤液化创新方法的科学和技术可行性研究。液化对建筑环境造成的破坏可能是灾难性的。在过去的四十年里，人们已经做出了大量的努力来了解液化的机制，并制定了在给定地震事件中分析一个地点液化潜力的程序。虽然液化的研究仍在继续，但岩土工程实践已经开发出各种现场改进技术，可以减轻液化的潜在影响。这种缓解措施费用昂贵，而且往往只能用于新项目。减轻液化对城市社区现有结构造成的损害仍然是一个重大挑战。其概念是在饱和的砂土中引入空气，以增加其抗液化能力。实验室和现场经验表明，在完全饱和的砂土中，只要有少量的空气（足以使饱和程度降低1%至2%），就可以显著提高液化强度，并降低剪切波速。因此，通过空气夹持，可以潜在地改善新的或现有的站点以抵抗液化，并且通过横波速度测量，可以验证其充分性。该研究有若干具体目标，旨在初步了解气包砂的行为，并确定未来研究的重要领域，以便将这一概念推进为缓解液化的充分发展和切实可行的措施。研究的目的可以用问题的形式表述如下：1。在松软的饱和砂土中如何引入空气？如何制备不同饱和度（从95%到100%）的样品？如何准确测量饱和度（最高0.1%）？空气夹持对液化强度有何影响？空气的存在对土壤的其他性质有什么影响？砂土的粒度分布和角度对上述结果有何影响？在不同的气流梯度下，空气能滞留多长时间？这项研究将对制定具有成本效益的减轻液化措施作出重大贡献。它还将对提高减少地震给社区造成的预期损失的能力产生更广泛的影响。该研究将利用地球环境领域的专门知识，利用空气注入进行修复。

0234365, Mishac Yegian, Northeastern University"Air Entrapment for Liquefaction Mitigation"This action is to support a study of the scientific and technical feasibility of an innovative approach for mitigating soil liquefaction.Liquefaction-induced damage to the built environment can be catastrophic. During the past four decades, intensive efforts have been made to understand the mechanism of liquefaction, and to develop procedures for analyzing the liquefaction potential at a site during a given seismic event. While research on liquefaction continues, geotechnical engineering practice has developed various techniques for site improvement that can mitigate the potential effects of liquefaction. Such mitigation measures are expensive, and often can only be utilized for a new project. Mitigating the liquefaction-induced damage to an existing structure in an urban community remains a major challenge.The concept is to introduce air in a saturated sand deposit to increase its resistance against liquefaction. Laboratory and field experiences suggest that only slight amounts of air in the voids of otherwise fully saturated sands (enough to reduce the degree of saturation by 1 to 2%) can significantly increase the liquefaction strength, and decrease the shear wave velocity. Hence, through air entrapment, a new or an existing site can potentially be improved to resist liquefaction, and through shear wave velocity measurements, its adequacy can be verified.The research has a number of specific objectives that are aimed at providing a preliminary understanding of the behavior of air-entrapped sands, and of identifying important areas for future research that would be needed to advance the concept to a fully developed and practical measure for liquefaction mitigation. The objectives of the research can be stated in the form of questions as follows:1. How can air be introduced in loose saturated sands?2. How can samples of varying degrees of saturation (from 95 to 100%) be prepared?3. How can the degree of saturation be measured accurately (up to 0.1%)?4. How will air entrapment affect the liquefaction strength?5. How are other soil properties influenced by the presence of air?6. How does the grain size distribution and angularity of the sand influence the above results?7. How long can air stay trapped under different flow gradients?The research will be a significant contribution to the development of cost-effective measures for liquefaction mitigation. It will also have a broader impact on improving the ability to reduce the expected losses to a community from an earthquake. The research will draw upon the expertise in the geo-environmental field that uses air injection for remediation.