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

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.