A METHOD FOR DETERMINATION OF WATER CONTENT IN REAL AND MODEL POROUS MEDIA IN EQUILIBRIUM WITH BULK ICE OR GAS HYDRATE

Vladimir Istomin, Evgeny Chuvilin, Boris Bukhanov, Tsutomu Uchida

Dans les comptes rendus d’articles de la conférence: GeoQuébec 2015: 68th Canadian Geotechnical Conference & 7th Canadian Permafrost Conference

Session: Laboratory Testing in Cold Regions / Essais en laboratoire en ingénierie nordique

ABSTRACT: A method for estimation of water content in porous media in equilibrium with bulk ice or gas hydrate is discussed. Measurements of water potential (and/or thermodynamic activity of water) were carried out on the Decagon company WP 4 device. Two types of porous media were used: the kaolinite clay and the artificial samples with known sizes of pores (controlled pore glasses - CPG). On the base of experimental determination of water potential in porous media the thermodynamic schemes are considered for: 1- confined water ; 2) nonclathrated water confand pressure of gas hydrate-former (methane, natural gas, etc.). The model is applied for estimations the unfrozen and nonclathrated water contents in the pore samples.

RÉSUMÉ: Un procédé pouDecagon WP 4. Deux types de milieux poreux ont été utilisés : des échantillons artificiels dont la taille des pores est connue (verre à porosité contrôlée de détermination expérimentale du potentiel hydrique dans des sols, les systèmes thermodynamiques sont considérés eau confinée dans le milieu poreux hydrophile » en fonction de la température (pour des températures négatives en Celsius); 2) « hydrate de gaz eau confinée dans le milieu poreux hydrophile » en fonction de la température et de la pression des timer la teneur en eau interstitielle non gelée et non clathratée des échantillons. 1. INTRODUCTION Water phase in porous media can exist in liquid state (capillary and film water) as well as in solid state (ice or gas hydrate). Unfrozen water in frozen soils affect on its physic-chemical and mechanic properties. In geocryology was developed various methods for determining the unfrozen water content (i.e. pore water in equilibrium with the ice) depending on the negative temperature (in centigrade) of the frozen soil (Tsytovich, 1975; Williams & Smith, 1989; Yershov, 1998). For many years researchers have attempted to develop predictive formulas for evaluating the content of unfrozen water in the frozen soils in the range of negative temperatures (Anderson & Tice,1972; Watanabe & Mizoguchi, 2002; and others). In recent years, the interest to quantitative evaluation of phase composition of moisture in frozen sediments has considerably increased (Istomin et al., 2009; Qin et al., 2009; Painter & Karra, 2014). This is due to development of new methods of experimental investigations of pore water and phase equilibria in frozen soils. Pore water may also exist in hydrate-containing soils. The pore water which is in equilibrium with gas hydrate phase we named as nonclathrated water. The term nonclathrated water was recently introduced (Chuvilin et al., 2011; Chuvilin & Istomin, 2012) in comparison of unfrozen water. In distinguishing from unfrozen water the nonclathrated water content depends not only the type of porous media and temperature, but in the greater degree

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