A STUDY ON THE PROPAGATION CHARACTERISTICS OF SURFACE WAVES IN GRANITE BASED ON ULTRASONIC MEASUREMENTS

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  • KIMOTO Kazushi
    岡山大学　環境生命科学研究科
  • OKANO Aoi
    岡山大学　環境生命科学研究科
  • SAITOH Takahiro
    群馬大学大学院理工学府　環境創生部門
  • SATO Tadanobu
    神戸学院大学・ 現代社会学部・ 防災社会学科
  • MATSUI Hiroya
    日本原子力研究開発機構・ 幌延深地層研究センタ ー・ 堆積岩処分技術開発 Gr

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Other Title
  • 超音波計測に基づく花崗岩中の表面波伝播特性に関する研究

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<p>This study investigates the propagation characteristics of surface wave traveling in a random heterogeneous medium. For this purpose, ultrasonic measurements are performed on a coarse-grained granite block as a typical randomly heterogeneous medium. In the ultrasonic testing, a line-focus transducer is used to excite ultrasonic waves, whereas a laser Doppler vibrometer is used to pickup the ultrasonic motion on the surface of the granite block. The measured waveforms are analysed in the frequency domain to evaluate the travel-time for each measurement point based on the Fermat’s principle. From the ensemble of travel-times obtained thus, the probability distribution of the travel-time is established as a function of travel-distance.The uncertainty of the travel-time and its spatial evolution are then investigated using the standard deviation of the travel-time as a measure of the uncertainty. As a result, it was found that the uncertainty is approximately proportional to the mean travel-time divided by the square root travel-distance.This is a finding that would be useful for stochastic modeling of the waves in random heterogeneous media.</p>

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