Evaluating Ground Liquefaction Potential by Piezovibrocone

通过压电振动锥评估地面液化潜力

• 批准号: 9810465
• 负责人: James Mitchell
• 金额: $ 9.5万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-07-15 至 2001-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9810465&HistoricalAwards=false
• 关键词: Evaluating; Ground; Liquefaction; Potential; Piezovibrocone

9703736 The objectives of this research program are to develop new instrumentation, test methodology, data acquisition, and field procedures for the direct in-situ and site-specific assessment of soil liquefaction potential by cone penetration testing. The program consists of a collaborative group effort between Georgia Tech and Virginia Tech, and is being co-funded with the United States Geological Survey. It includes the assembly of a vertically-vibrating piezocone penetrometer (piezovibrocone), laboratory calibration chamber testing, a companion series of laboratory cyclic triaxial and simple shear testing, and field trials at geotechnical experimentation sites. Current methods of assessing the liquefaction susceptibility of loose sands and silts during earthquake shaking rely strongly on empirical correlations and methodologies. Present state-of-practice procedures for liquefaction evaluation include both in-situ and laboratory test methods that require correction factors which are not fully understood, nor well defined. The vibrocone consists of a cone penetrometer coupled with a vibrating shaker mechanism that induces liquefaction of the soil in the vicinity of the probe during penetration into the ground. Vertical penetration tests are conducted under both static and dynamic excitation in paired side-by-side soundings. Comparisons of cone tip resistance values, sleeve friction values, and penetration pore water pressures from adjacent soundings are made to ascertain the liquefaction potential and other properties of the subsoils. The penetration test is designed to allow a rational interpretation by analytical theories which incorporate important soil behavioral aspects such as dynamic loading, cyclic pore pressure generation, initial stress state, and residual undrained steady- state strength. As envisioned, the piezovibrocone will thus offer an improved and systematic framework for evaluating the liquefaction susceptibility of loos e ground in seismically-active regions. Additionally, it should have value for assessing the applicability and effectiveness of ground modification techniques such as vibroflotation, vibro-replacement, and densification by blasting.

9703736本研究计划的目标是开发新的仪器、测试方法、数据采集和现场程序，以便通过锥体渗透测试直接在现场和特定地点评估土壤液化潜力。该项目由佐治亚理工学院和弗吉尼亚理工学院组成，由美国地质调查局共同资助。它包括垂直振动压电锥贯入计的组装，实验室校准室测试，实验室循环三轴和简单剪切测试的配套系列，以及在岩土工程实验点的现场试验。目前评估松散砂和淤泥在地震中液化敏感性的方法在很大程度上依赖于经验相关性和方法。目前液化评价的实践状态程序包括现场和实验室测试方法，这些方法需要校正因子，而这些校正因子没有得到充分理解，也没有得到很好的定义。该测振器由一个锥形贯入仪和一个振动激振器组成，该激振器在探入土中引起探头附近土壤的液化。垂直侵彻试验在静态和动态两种激励下进行。通过比较相邻探测所得的锥尖阻力值、滑套摩擦值和渗透孔隙水压力，确定了地基的液化潜力和其他特性。渗透试验的目的是通过分析理论来合理解释，这些理论结合了重要的土壤行为方面，如动载荷、循环孔隙压力产生、初始应力状态和残余不排水稳态强度。正如所设想的那样，压电振镜将因此为评估地震活跃地区地面的液化易感性提供一个改进的和系统的框架。此外，它应该对评估振冲、振冲替代和爆破致密化等地面改造技术的适用性和有效性有价值。