Energy-based Approach for Evaluating and Mitigating Liquefaction Potential

这笔赠款为开发一种基于能源的方法提供资金，以评估液化触发的可能性和设计补救致密化计划。将作为本研究的一部分开发的基于力学的液化评估程序将建立在现有的宏观水平，低周，金属疲劳理论，使用耗散能量作为其损伤度量。然后，将在贝叶斯框架内使用现场案例历史和实验室数据对该程序进行校准。使用耗散的能量（即，由剪切应力、剪切应变滞后回线限定的累积面积）作为损伤度量具有物理意义。能量主要耗散在桑迪土壤中，所述沙质土壤通过由沙粒的相对运动引起的颗粒间摩擦而经受震动（即，土壤骨架的分解）。由于该过程将基于完善的疲劳理论，因此将更容易校准在当前液化/非液化情况历史数据库中不强烈存在的条件（例如，高有效围压应力和非美国西部的地面运动）。此外，该程序将能够评估受到地震以外的运动的土壤的液化潜力（例如，施工振动、补救致密化技术）。如果成功的话，这项研究的结果将有助于通过改进目前的液化风险评估和缓解方法来最大限度地减少地震造成的损失。一种可以自信地用于评估除活跃地壳浅部区域（即，在美国西部以外的地区，例如美国中东部）对工程专业有直接影响。该项目是特别及时的，因为国家重新对核电的兴趣，因为大多数新工厂将位于美国西部以外。

This grant provides funding for the development of an energy-based approach for evaluating the potential for liquefaction triggering and for designing remedial densification plans. The mechanically-based liquefaction evaluation procedure that will be developed as part of this study will build on existing macro-level, low-cycle, metal fatigue theories, using dissipated energy as its damage metric. The procedure will then be calibrated using field case histories and laboratory data in a Bayesian framework. Using dissipated energy (i.e., cumulative area bound by the shear-stress, shear-strain hysteresis loops) as a damage metric has physical significance. Energy is primarily dissipated in sandy soil that is subjected to shaking by inter-particle friction resulting from the relative movement of the sand particles (i.e., breakdown of the soil skeleton). Because the procedure will be based on well established fatigue theories, it will be easier to calibrate for conditions that do not have a strong presence in current liquefaction/non-liquefaction case history databases (e.g., high effective confining stresses and non-western U.S. ground motions). Additionally, the procedure will be able to evaluate liquefaction potential of soils subjected to motions other than those from earthquakes (e.g., construction vibrations, remedial densification techniques). If successful, the results of this research will help minimize losses from earthquakes by improving the current methods for liquefaction risk assessment and mitigation. A procedure that can be confidently used to evaluate liquefaction potential in tectonic regimes other than active shallow crustal regions (i.e., in regions other than the western U.S., for example the central-eastern U.S.) will have direct impact on the engineering profession. The project is particularly timely as the nation renews its interest in nuclear power because most of the new plants will be located outside of the western U.S.