In order to study the transmitting characteristics of ultrasonic guided wave in partly embedded guardrail post and select the suitable guided waves mode and frequency for inspecting post length, authors calculated and analyzed the guide wave group velocities, attenuation and dispersion in unembedded part and buried part of the posts respectively on the basis of elastic dynamics theory. Results show that the group velocities of longitudinal mode L(0, 2) are the same in the frequency range of 80 kHz to 130 kHz for the unembedded part and embedded part of the posts. L(0, 2) mode can propagate enough long distance in the post so that it can be used to measure the length of posts partly embedded in soil because its attenuation is the lowest in all modes. At the same time, the experiment result is consistent with results of theoretical analysis. Waveform of end echo is clear and has high signal-to-noise ratio. The maximal relative error is less than 0.8%. This method can meet the needs of engineering application.
Key words
road engineering /
guardrail post /
ultrasonic guided wave technology /
inspection of length partly embedded in soil /
elastic dynamics
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