Evaluating Ground Liquefaction Potential by Piezovibrocone

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的直接原位和现场特定的土壤液化潜力的评估锥贯入试验。 该项目由格鲁吉亚理工学院和弗吉尼亚理工学院的合作小组组成，并与美国地质调查局共同资助。它包括一个垂直振动的piezo-vibrocone（piezo-vibrocone），实验室校准室测试，一个同伴系列的实验室循环三轴和简单的剪切测试，并在岩土实验场地的现场试验组件。 目前的方法评估松散的砂和粉土在地震震动液化敏感性强烈依赖于经验的相关性和方法。目前液化评价的实践程序包括现场和实验室测试方法，这些方法需要修正系数，但这些修正系数尚未完全了解，也没有很好地定义。 该振动锥由一个锥孔流量计和一个振动振动器组成，振动器在探头插入地面的过程中引起探头附近土壤的液化。垂直贯入试验在静态和动态激励下进行，成对并排测深。锥尖阻力值，套筒摩擦值，并从相邻的探测渗透孔隙水压力的比较，以确定液化潜力和其他属性的底土。贯入试验旨在通过分析理论进行合理解释，分析理论结合了重要的土壤行为方面，如动态荷载、循环孔隙压力生成、初始应力状态和残余不排水稳态强度。如所设想的，压电振动锥将因此提供一个改进的和系统的框架，用于评估液化的易受影响性松散的地面在地震活跃的地区。此外，它应该有价值的评估的适用性和有效性的地面改造技术，如振冲，振动置换，并通过爆破密实。

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.