不同入射频率下超声波横波在砂岩中的传播特性研究

    PROPAGATION CHARACTERISTICS OF ULTRASONIC SHEAR WAVE IN SANDSTONE UNDER DIFFERENT INCIDENT FREQUENCIES

    • 摘要: 岩石中超声波横波声学参数与力学参数密切相关,利用超声波横波传播特性可以反演岩石力学参数,但目前相关研究成果较少,因此需要深入开展岩石中超声波横波传播特性的研究。本文以灰砂岩、红砂岩和黄砂岩为研究对象,开展50 kHz、100 kHz和200 kHz频率下超声波横波传播试验;提取波速、主频和最大幅值等声学参数进行砂岩中超声波横波的传播特性研究;通过归一化处理,分析了3种声学参数对弹性模量变化的敏感性。结果表明,在3种砂岩中,横波波速、主频都随入射频率和弹性模量增大呈非线性递增趋势,最大幅值随入射频率呈降低趋势,而弹性模量和入射频率对3种声学参数变化率的影响呈现出不同规律;整体分析发现最大幅值对砂岩弹性模量变化的敏感性最强,基于最大幅值建立了砂岩弹性模量的估算公式;基于波形、信噪比、相关性的综合考虑,建议今后采用50 kHz作为砂岩超声波横波测试的入射频率。研究成果可以为超声波测试技术的发展提供参考。

       

      Abstract: The acoustic parameters of ultrasonic shear waves in rocks are closely related to mechanical parameters. The mechanical parameters of rocks can be inverted by using the propagation characteristics of ultrasonic shear waves. However,there are few relevant research results at present,so it is necessary to carry out in-depth research on the propagation characteristics of ultrasonic shear waves in rocks. Taking grey,red and yellow sandstone as the research objects,carry out ultrasonic shear wave propagation experiments at frequencies of 50,100 and 200 kHz. We extract acoustic parameters such as wave speed,dominant frequency and maximum amplitude to study the propagation characteristics of ultrasonic shear waves in sandstone. The results show that in the three types of sandstones,the shear wave velocity and dominant frequency all show a nonlinear increasing trend with the increase of the incident frequency and elastic modulus,and the maximum amplitude decreases with the incident frequency. Through homogenization,the sensitivity of the three acoustic parameters to the change of elastic modulus is analyzed. The results show that in the three kinds of sandstone,the shear wave velocity,dominant frequency and maximum amplitude increase nonlinearly with the increase of incident frequency and elastic modulus,while the effects of elastic modulus and incident frequency on the change rates of three acoustic parameters show different laws. The overall analysis shows that the maximum amplitude is the most sensitive to the change of the elastic modulus of sandstone. Three estimation formulas for the elastic modulus of sandstone are established based on the maximum amplitude. 50 kHz is the incident frequency for ultrasonic shear wave testing of this type of sandstone. The research results can provide reference for the development of ultrasonic testing technology.

       

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