Static enthalpy equilibrium and the energetic stability of saturated granular systems

This work presents a physically motivated framework for the stability and instability of fully saturated granular systems based on a static enthalpy equilibrium (SEE) concept. In contrast to classical stress–strain or effective-stress-based approaches, the proposed formulation interprets liquefaction and densification as state transitions between energetically admissible configurations, governed by buoyancy, pore-fluid interaction, and geometric constraints of the granular skeleton. The paper develops the theoretical basis of SEE for saturated sands under isothermal conditions and shows how characteristic phenomena—such as spontaneous liquefaction, progressive densification, and post-liquefaction settlement—can be described consistently within a unified energetic framework. Particular emphasis is placed on the role of pore-fluid coupling, time-scale separation between grain rearrangement and fluid dissipation, and the existence of energetically preferred end states that are independent of loading history. The approach is positioned as complementary to classical soil mechanics, retaining compatibility with established concepts (e.g. consolidation and pore-pressure dissipation) while providing an alternative interpretation of instability that does not rely on predefined failure criteria or strain localization assumptions. The framework is intended to support both laboratory-scale interpretation and field-scale reasoning for liquefaction-related ground deformations. This manuscript is provided as an author preprint to ensure transparency, citability, and long-term accessibility. The work is not under active review elsewhere at the time of publication and may serve as a basis for subsequent extended or journal-specific versions.