| 講演要旨(和文) | | 本研究では、多孔質媒体内の孔隙内で成長する固液共存系が超音波伝播、ここではP波ならびにS波、にどのような影響を及ぼすのか室内実験により確かめた。アルミナを主成分とするセラミックフィルタを塩水で飽和させたものを20度から-15度まで低温化する過程において、周波数150から1000Hzまでの超音波データを取得した。減衰解析を行った結果、凝固点付近を境にして、減衰減少の傾向が異なることを見いだした。また、3回の再現性実験を試みたところ、初動波形は再現性が確保されていたが、後続波の再現性はみられなかった。このことは、孔隙内に生成される固液共存系は毎回賦存状況が異なることの可能性があることを示唆し、このことが有益な情報になりえるだろう。 |
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| | 講演要旨(英文) | | Ultrasonic wave transmission measurements were conducted in order to examine the influence of ice-brine coexisting system grown in porous material on ultrasonic P- and S-waves. We observed the variations of a transmitted wave with a frequency content of 150-1000 kHz through a liquid system to a solid-liquid coexistence system, changing its temperature from 20C to -15C. We quantitatively estimated attenuation for porous materials with two different porosities during the freezing of salty water in porous material by considering different distances between the source and receiver transducers. This paper is concerned with attenuation at ultrasonic frequencies of 500-1000 kHz for P-waves and 100-400 kHz for S-waves. The laboratory experiments of the present study demonstrated that ultrasonic waves with such a frequency range are significantly affected by the existence of a solid-liquid coexistence system in the porous material. Our repeatability test indicates that small changes occurred in porous media may influence on the observed waveform, especially in later phase. |
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