Energy-Based Model for Excess Pore-Water Pressure Generation in Saturated Coral Sand

The liquefaction behavior of saturated coral sand exhibits a distinct mechanical transformation that can be characterized by two successive phases: a solid–liquid transition phase dominated by solid-like behavior and a pseudofluid phase governed by fluid-like responses. The threshold excess pore-water pressure (EPWP) ratio at the phase transition ( r u , th ) is approximately 0.90. Recognizing the intrinsic coupling between energy dissipation and EPWP generation during undrained shearing, a conversion efficiency parameter, ω (defined as Δ r up /Δ W s,i ), is introduced in this study to quantify the relationship between incremental energy dissipation (Δ W s,i ) and the corresponding peak EPWP ratio increment (Δ r up ). In a semilogarithmic framework, ω exhibits a negative linear correlation with the peak EPWP ratio ( r up ) during the solid–liquid transition stage, whereas a negative power–law relationship is observed in the pseudofluid stage. Notably, the ω – r up relationship is largely insensitive to loading parameters, including cyclic stress ratio, loading direction angle ( α σ ), and loading frequency ( f ), but is significantly influenced by particle gradation, consolidation conditions, and sand type. Based on these observations, a phased energy-based model for EPWP generation is developed. The proposed model effectively captures the evolution of energy conversion during liquefaction and provides a robust theoretical basis for energy-informed evaluation of in situ soil strength using laboratory-derived data.