Evaluation of Field-Based Liquefaction Approaches for Calcareous Sands Using Shear Wave Velocity

使用剪切波速度评估钙质砂的现场液化方法

• 批准号: 1234780
• 负责人: Christopher Baxter
• 金额: $ 18.95万
• 依托单位: University of Rhode Island
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2015-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1234780&HistoricalAwards=false
• 关键词: Evaluation; Field; Based; Liquefaction; Approaches

The objective of this project is to assess the applicability of current field-based liquefaction approaches for calcareous sands. This is of importance because there are many coastal communities in areas of high seismicity founded on calcareous sands (e.g. Haiti, Puerto Rico, Hawaii, etc.), and existing field-based approaches were developed almost entirely for case studies in silica sands. We will perform a combined in situ and laboratory-testing program at two sites in western Puerto Rico, which is an ideal site because of the extent of calcareous deposits throughout the island, the relatively high seismicity of the region, the high population density, and the expertise of the research team with these particular soils. The in situ testing program will consist of conventional drilling and sampling techniques, Standard Penetration Tests with hammer energy measurements, and Cone Penetration Testing with shear wave velocity measurements. The laboratory-testing program will consist of cyclic triaxial and cyclic simple shear tests with shear wave velocity measurements. Research by the PIs has shown that the relationship between cyclic resistance and shear wave velocity (CRR-Vs) is soil specific and can be used to link in situ test results with laboratory determined values of CRR. Shear wave velocity (Vs) has been shown to be a good measure of the combined effects of stress and fabric, and it is hypothesized that samples consolidated or prepared to in situ values of Vs yield the in situ CRR. This approach will be used to estimate the in situ CRR at each site by linking the shear wave velocity in the laboratory and the field, and then comparing this with values of CRR predicted from existing field based approaches (SPT, CPT). This research will lead to a better understanding of how existing field based correlations for the assessment of liquefaction potential, which is the state-of-the-practice in geotechnical earthquake engineering, applies to calcareous sands that can be found in many tropic and subtropical coastal regions. In addition, this project will build upon existing research that shows that shear wave velocity measured appropriately in the laboratory and in situ can provide a link between laboratory testing and field measurements for characterizing the in situ behavior of soils that are difficult to sample. The primary societal impact of this research will be to help minimize losses from earthquakes by improving the current methods for liquefaction potential assessment in calcareous sands. Another important component of this project is the inclusion of students from underrepresented groups in the STEM fields of research. Three Hispanic American students from Puerto Rico will be working on this research project. One Hispanic American from Puerto Rico is currently a Ph.D. student at the University of Rhode Island and will complete her dissertation on the proposed research. Two undergraduates will work on this project as summer research assistants through an existing collaboration between the PI, University of Puerto Rico Mayaguez, and the University of Rhode Island Transportation Center as part of the Federal Highway Administration Dwight D. Eisenhower Fellowship Program.

该项目的目的是评估当前钙质砂现场液化方法的适用性。 这一点很重要，因为在地震高发地区有许多沿海社区建立在钙质砂上（例如海地、波多黎各、夏威夷等），而现有的基于现场的方法几乎完全是针对硅砂的案例研究而开发的。 我们将在波多黎各西部的两个地点进行现场和实验室测试相结合的项目，这是一个理想的地点，因为全岛钙质沉积物范围广泛，该地区的地震活动相对较高，人口密度高，并且研究团队对这些特殊土壤的专业知识。 现场测试计划将包括传统的钻孔和取样技术、使用锤能量测量的标准渗透测试以及使用剪切波速度测量的锥体渗透测试。 实验室测试计划将包括循环三轴和循环简单剪切测试以及剪切波速度测量。 PI 的研究表明，循环阻力和剪切波速 (CRR-Vs) 之间的关系是特定于土壤的，可用于将现场测试结果与实验室确定的 CRR 值联系起来。 剪切波速 (Vs) 已被证明是应力和织物综合效应的良好衡量标准，并且假设固结或制备成原位 Vs 值的样品产生原位 CRR。 该方法将用于通过将实验室和现场的剪切波速度联系起来来估计每个地点的原位 CRR，然后将其与现有基于现场的方法（SPT、CPT）预测的 CRR 值进行比较。这项研究将有助于更好地理解现有的基于现场的液化潜力评估相关性如何应用于许多热带和亚热带沿海地区的钙质砂，这是岩土地震工程的最新实践。地区。 此外，该项目将建立在现有研究的基础上，现有研究表明，在实验室和原位适当测量的剪切波速度可以提供实验室测试和现场测量之间的联系，以表征难以采样的土壤的原位行为。 这项研究的主要社会影响将是通过改进现有的钙质砂液化潜力评估方法，帮助最大限度地减少地震造成的损失。 该项目的另一个重要组成部分是将来自代表性不足群体的学生纳入 STEM 研究领域。 来自波多黎各的三名西班牙裔美国学生将参与这个研究项目。 一位来自波多黎各的西班牙裔美国人目前是博士学位。罗德岛大学的学生，并将完成有关拟议研究的论文。 作为联邦公路管理局德怀特·D·艾森豪威尔奖学金计划的一部分，两名本科生将通过 PI、波多黎各马亚格斯大学和罗德岛大学交通中心之间的现有合作，作为夏季研究助理参与该项目。