Experimental study on acoustic propagation spectrum characteristics of rocks under high water pressure and high stress

The deep rock mass is in the environment of high water pressure and high ground stress, and its damage evolution characteristics are affected by the occurrence environment. Acoustic wave is widely used to characterize the damage cumulative evolution degree of rocks. In order to study the rule and attenuation mechanism of acoustic wave propagation of rocks under high water pressure and high stress, based on a self-developed high water pressure and high stress rock acoustic wave testing system, 6 water pressure and 5 axial static stress levels were set to simulate the deep engineering environment, and acoustic wave propagation tests were carried out on red sandstone and limestone with large porosity differences. The selection method of the head wave was determined and the head wave was analyzed by the Fourier transform. The frequency domain transmission coefficient was defined, and the variation rules of the transmission coefficient, the centroid frequency and the quality factor were analyzed. The relationship between the wave impedance and the quality factor was explored and the empirical models of rocks frequency-domain attenuation were built. The empirical models of rock frequency-domain attenuation were built. The results show that the acoustic spectrum area and transmission coefficient of red sandstone firstly increase and then decrease with the increase of the water pressure, and the water pressure and transmission coefficient have Gaussian function relationship. While the two parameters of limestone first increase then change slightly with the increase of the water pressure. The transmission coefficient of two kinds of rocks both increase first and then decrease with the increase of the axial static stress. With the increase of water pressure, the centroid frequency of red sandstone decreases linearlyand the“frequency drift”phenomenon appears, while that of limestone increases first and then decreases slowly. With the increase of axial static stress, the centroid frequency of different rocks first increase and then decrease. With the increase of water pressure, the quality factors of the two rocks first increase rapidly and then decrease, but the degree of decrease are different, the red sandstone decreases significantly, and the limestone decreases slightly. When the red sandstone and limestone are in the compaction stage, the quality factor increases, and when the rocks reach the damage stage, the quality factor decreases. The research results provide a theoretical basis for exploring acoustic research methods of rock damage evolution under deep high water pressure environment. © 2024 Academia Sinica. All rights reserved.