Energetic Stability of Saturated Granular Packings under Buoyancy: A Landau-Type Formulation of Static Enthalpy Equilibrium

This paper presents a Landau-type formulation of the stability of saturated granular packings based on the concept of Static Enthalpy Equilibrium (SEE). The framework describes the existence of a load-bearing granular skeleton in terms of an effective energy landscape, in which porosity acts as an order parameter and instability corresponds to a spinodal condition defined by vanishing curvature. The formulation provides a physically transparent connection between geotechnical observations of liquefaction and concepts of metastability and jamming in granular physics. Saturated granular packings can sustain mechanical loads through a network of grain contacts forming a load-bearing skeleton. However, loose packings may abruptly lose their structural integrity and undergo rapid rearrangement, as observed in spontaneous liquefaction. In this work, the stability of saturated granular systems is formulated in terms of an effective energy landscape, in which porosity acts as a macroscopic order parameter describing the structural state of the packing. The effective energy results from the competition between structural resistance of the grain contact network and buoyancy-reduced gravitational energy. The gravitational contribution increases strongly with porosity and can be approximated by a term proportional to 1/(1 − n). Within this framework, a stable granular skeleton corresponds to a metastable minimum of the energy landscape. Instability occurs when the curvature of the energy landscape vanishes, corresponding to a spinodal condition. This formulation provides a physically transparent description of stability in athermal granular systems and establishes a connection between geotechnical observations of liquefaction and concepts of metastability and jamming in granular physics.