超声波速度测定中影响因素的实验研究.docVIP

 超声波速度测定中影响因素的实验研究# 赵闯，李成波，杨映系，施行觉** （中国科学技术大学 地球和空间科学学院） 5 10 摘要：超声波测波速时，会受到样品长度、换能器频率、信号放大倍数以及耦合剂和耦合力 等因素影响。为了定量地了解这些因素对测量结果的影响，本文用频率为 550k 和 50kHz 二 种换能器分别测量了近百块不同长度的干燥样品的波速。发现波速随长度的变化由一维“杆” 中的波速逐渐增大并稳定在三维“无限大”中的波速；一定长度后，频散趋于稳定且与样品 Q 值有关；波速随信号放大倍数、耦合剂及耦合强度增大而增大。实验数据与波动理论、波 速频散公式相符合。用频散法测量了 Q，与频谱振幅比法结果有 1～11%相差；对分别用地 震仪和声波仪测得的岩体完整性系数经频散修正后，二者平均值之差由 8%降到 1.4%。 关键词：固体地球物理;超声波速度; 频散 ;衰减 ;岩体完整性系数 中图分类号：P315 15 The Laboratory study of influence factors during ultrasonic velocity measurement ZHAO Chung, LI Chengbo, YANG Yingxi, SHI Xingjue (School of Earth and Space Sciences, University of Science and Technology of China) 20 25 30 Abstract: IDuring ultrasonic velocity measurements, the result would be affected by the length of the samples, the transducer’s frequency, signal amplification, coupling agents, coupling strength and other factors. In order to quantitatively understand these factors on the results, in this paper, two different frequencies (550kHz, 50kHz) transducers measured the velocities of nearly a hundred samples with different lengths. It was found that, with the increase of the length, the velocity changed from the velocity of one-dimensional bar to the velocity of three-dimensional infinity。 After a certain length, dispersion became a stable value which related to the sample’ s Q; velocity increased with the signal amplification, coupling agents and coupling strength. The results were consistent with the wave theory and dispersion formula. By the dispersion formula, the results of Q from dispersion method had a difference of 11% according to the spectral amplitude ratio method for the samples. After the dispersion correction, the average difference between the coefficient of rock mass integrity tested by seismograph and the one by acoustic instrument decreased to 1.4% from 8%. Key words: Sollid Geophysics; ultrasonic velocity, dispersion, attenuation, the coefficient of rock mass integrity 35 0 引言 迄今为止，地震波是研究地球内部最有效地工具 [1] ，,岩石中弹性波速度是联系岩石性