Energy-based Approach for Evaluating and Mitigating Liquefaction Potential

这笔赠款为发展一种以能源为基础的方法提供资金，以评估触发液化的可能性和设计补救性致密化计划。作为本研究的一部分，将开发的基于机械的液化评估程序将建立在现有的宏观水平、低周期、金属疲劳理论基础上，使用耗散能量作为其损伤度量。然后将使用贝叶斯框架中的现场病例历史和实验室数据对该程序进行校准。使用耗散能（即受剪切应力、剪切应变迟滞回线约束的累积面积）作为损伤度量具有物理意义。能量主要在沙质土壤中耗散，沙质土壤受到由沙粒相对运动引起的颗粒间摩擦的震动（即土壤骨架的破坏）。由于该程序将基于完善的疲劳理论，因此将更容易校准当前液化/非液化案例历史数据库中不存在的条件（例如，高效围应力和非西部美国地面运动）。此外，该程序将能够评估受地震以外的运动（例如，建筑振动，补救致密化技术）影响的土壤的液化潜力。如果成功，这项研究的结果将通过改进目前的液化风险评估和减轻方法，帮助最大限度地减少地震造成的损失。一个可以自信地用于评估除活跃的浅层地壳区域（即，除美国西部以外的地区，例如美国中东部）以外的构造区液化潜力的程序将对工程专业产生直接影响。随着美国重新燃起对核能的兴趣，这个项目显得尤为及时，因为大多数新核电站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.