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Phase Equilibrium Condition for Pore Hydrate: Theoretical Formulation and Experimental Validation
Author(s) -
Zhou Jiazuo,
Liang Wenpeng,
Wei Changfu
Publication year - 2019
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2019jb018518
Subject(s) - hydrate , thermodynamics , thermodynamic equilibrium , pore water pressure , materials science , capillary pressure , dissociation (chemistry) , chemistry , geotechnical engineering , porous medium , geology , porosity , composite material , physics , organic chemistry
Based on the chemical potential equilibrium of water, a generalized equation of phase equilibrium is presented for pore hydrate, which relates the temperature depression of hydrate to the capillary pressure and osmotic pressure. The relationship between capillary pressure and unhydrated water content can be characterized by a soil‐water characteristic curve (SWCC). Uniting the SWCC and the phase equilibrium equation yields the equation of soil hydration characteristic curve (SHCC), which expresses the relationship between the unhydrated water content and temperature depression of pore hydrate. A series of experiments are performed, validating the phase equilibrium equation and the concept of SHCC. From the SHCC, the phase equilibrium surface can be determined in the space of temperature, pressure, and unhydrated water content. The thermodynamic state of pore hydrate moves on the equilibrium surface when the hydrate forms or dissociates. The projections of the equilibrium surface indicate the dissociation process of pore hydrate caused by thermal stimulation or depressurization. The salt solution changes the equilibrium surface to the direction that requires lower temperature and higher pressure and slows down the dissociation rates of hydrate to temperature and pressure.