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| | 講演要旨(英文) | | We conducted experimental study to understand the ultrasonic wave propagation properties in porous sand saturated with brine. We measured P-wave and S-wave velocities in porous sand that incorporates partially frozen brine by using conventional pulse transmission technique. Compressional and shear wave velocity measurements were carried out in unconsolidated sand that is saturated with brine with salinity 2%. Observations were carried out with decreasing temperature from 25oC to -20oC. We observed sudden increase in compressional wave velocity at around -3oC. At a lower temperature, unfrozen brine is embedded inside micro pores in ice, with exhibiting solid-liquid co-existing system. We also conducted pulsed nuclear magnetic resonance (NMR) in partially frozen brine to observe characteristics of unfrozen brine during the temperature decrease. NMR observation is carried out by using instrument JEOL JNM-MU25 with frequency 25Mz. We observed the spatial distribution of pore size and unfrozen brine mobility in partially frozen brine at temperature range from -3oC to -12oC respectively. |
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