中文摘要：

为了研究导波在半埋地护栏立柱结构中的传播特性，并从中选择适合检测立柱长度的导波模态和频率，在弹性动力学理论基础上，分别对立柱未埋地部分和埋地部分的导波群速度、衰减和频散进行计算分析。结果表明：80～130kHz的纵向模态L（0，2）在未埋地部分和埋地部分中的群速度相同，衰减程度最小，传播距离可以满足检测要求，可以用来对半埋地立柱埋深进行检测；试验验证结果和理论分析相吻合，所获得的端面回波信号清晰，有较高的信噪比，测量的最大相对误差小于0．8％，可以满足工程实际要求。

英文摘要：

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