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.
