Evaluating Ground Liquefaction Potential by Piezovibrocone

9703736这项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，以便通过圆锥贯入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合作完成，并与美国地质调查局共同出资。它包括组装一台垂直振动的压电式压电式贯入仪、实验室定标室测试、配套的一系列实验室循环三轴和简单剪切测试，以及在岩土试验现场的现场试验。目前评估松散砂土和粉土在地震震动过程中液化敏感性的方法主要依赖于经验相关性和方法学。目前用于液化评估的实用程序包括现场测试方法和实验室测试方法，这些方法需要修正系数，但这些修正系数既没有完全理解，也没有很好地定义。可控震源由一个锥形贯入仪和一个振动振动器组成，振动器机构在钻入地面时在探头附近引起土壤液化。垂直贯入试验是在成对的并排测深中，在静态和动态激励下进行的。为了确定地基土的液化势和其他性质，对相邻测深的锥尖阻力值、套筒摩擦值和贯入孔压进行了比较。渗透试验的设计是为了通过分析理论进行合理的解释，这些分析理论包含了重要的土性方面，如动态荷载、循环孔压产生、初始应力状态和剩余不排水稳态强度。正如所设想的那样，压电振动锥将因此为评估地震活跃区地面的液化敏感性提供一个改进的和系统的框架。此外，它对于评估振冲、振动置换和爆破致密化等地基处理技术的适用性和有效性也具有一定的价值。

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.