EXPERIMENTAL STUDY ON THERMOPHYSICAL PARAMETERS OF HIGH WATER GRAVEL FORMATION FOR FREEZING CONSTRUCTION

The thermophysical parameters of stratum must be clearly defined in the freezing method. This paper aims to ascertain the thermophysical parameters of water-rich gravel stratum and the interactions between the parameters and the influencing factors. It examines the effect of salt content on the initial freezing temperature of gravel samples and the interactions among freezing temperature, specific heat capacity and thermal conductivity of the samples based on their initial parameters measured by a self-made test device. The experimental results show that the increasing salt content leads to continuous decrease of the vapor pressure of water in the samples, which requires lower temperature and more energy for the samples to freeze. Specially, with the increase of salt content, the initial freezing temperature of the samples 1, 2 and 3 decreased from -0.46 to -1.15 ℃. With the decrease of freezing temperature, the ice content in the samples increased while the unfrozen water content decreased. Because the specific heat capacity of ice is half of that of water, the specific heat capacity of the samples decreased continuously from 1.60 J·(g·℃)^-1 to 1.06 J·(g·℃)^-1. Because the thermal conductivity of ice is much larger than that of water, the thermal conductivity of the samples increased from 1.71 W·(m·K)^-1 to 2.13 W·(m·K)^-1. As the ice content and unfrozen water content in the samples changed with temperature, the liquid-solid phase transformation of the water caused the variation in physical and mechanical properties of the samples.