Liquefaction as an energetic instability of saturated granular systems – Density control and static enthalpy equilibrium

Abstract

Liquefaction of saturated granular materials is commonly interpreted within stress-based frameworks that rely on the existence of an intact grain skeleton. At the onset of liquefaction, however, the contact network collapses and effective stress ceases to be a meaningful state variable. This work reformulates liquefaction as an enthalpy-driven instability of the coupled grain–water system and

Summary

This paper introduces a novel energetic framework called Static Enthalpy Equilibrium (SEE) to explain liquefaction in saturated granular materials. It reframes liquefaction as an instability triggered by exceeding an energy threshold, offering an alternative to traditional stress-based approaches, particularly when effective stress is no longer meaningful.

Key Insights

• •Liquefaction is triggered when the cumulative external energy input exceeds a porosity-dependent enthalpy barrier, independent of stress amplitude or cycle count, shifting the focus from stress to energy.
• •The grain skeleton collapses spontaneously due to the release of internal gravitational-buoyancy enthalpy, not continued external forcing, providing a new perspective on the collapse mechanism.
• •The framework introduces a density-controlled energetic limit, defining a stabilized porosity that depends solely on grain density, representing the point where no further pore-water pressure can be generated.
• •The SEE framework provides a unifying reinterpretation of established experimental findings, elevating the analysis from stress-based descriptors to an energetically defined state perspective.

Practical Implications

• •The SEE framework can potentially improve liquefaction risk assessment by providing a physically meaningful stability criterion, especially in situations where effective stress approaches are inadequate.
• •Future research should focus on developing experimental methods to measure the enthalpy barrier for different materials and validating the density-controlled stability limit across various soil types.
• •Integrating the SEE framework into numerical models could enhance the simulation of liquefaction events and improve the accuracy of liquefaction risk predictions in geotechnical engineering.
• •Further studies are needed to address the practical challenges of measuring or estimating the external energy input in real-world scenarios to facilitate the field application of this framework.

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