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Journal Articles

A Study on the propagation characteristics of surface waves in granite based on ultrasonic measurements

Kimoto, Kazushi*; Okano, Aoi*; Saito, Takayasu*; Sato, Tadanobu*; Matsui, Hiroya

Doboku Gakkai Rombunshu, A2 (Oyo Rikigaku) (Internet), 76(2), p.I_97 - I_108, 2020/00

AA2020-0209.pdf:2.72MB

This study investigates the propagation characteristics of surface wave traveling in a random heterogeneous medium. For this purpose, ultrasonic measurements are performed on a granite block as a typical randomly heterogeneous medium. In this measurement, 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, the probability distribution 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.

Oral presentation

A Study on the propagation characteristics of surface waves in a granite based on ultrasonic measurement

Kimoto, Kazushi*; Okano, Aoi*; Saito, Takayasu*; Sato, Tadanobu*; Matsui, Hiroya

no journal, , 

This study investigates the propagation characteristics of high frequency surface wave in a granite block by ultrasonic measurements. To this end, a surface wave field excited by a line-focus transducer is scanned finely over a rectangular aperture with a laser Doppler vibrometer. From the measured waveforms, the spatial distribution of Fourier phase is reconstructed, and the structure of the wave front system is investigated. Due to the heterogeneity of the granite, the wave fronts fluctuate spatially at a rate dependent on the ultrasonic frequency. The intensity of the fluctuation is then quantified as a local wavenumber vector. It was found as a result that the granite sample can be characterized by a random wave number whose probability density is frequency dependent, asymmetric and non-Gaussian having a finite support.

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