Abstract: The acoustic emission (AE) research of rock bridge failure is usually only based on the analysis of related parameters such as counting, energy and so on. In order to study the AE frequency spectrum characteristics of rock bridge in direct shear test, the characteristics of AE frequency spectrum are analyzed using time frequency analysis method. The results show that the amplitude is more obvious and the time of intense response is earlier compared with the counts rate in direct shear test. The AE dominant frequency is basically in the high and low frequency bands. The characteristics of the dominant frequency dispersing to intermediate and the low frequency having high amplitude can be used as precursor information of main fracture, and the former appears earlier. Compared with the result from uniaxial compression test, the amplitude in the main fracture stage is obviously different with intermediate frequency occurs at this time. The amplitude of AE is determined by the stress of particles, and the frequency is related to the final displacement of the particle force chain. With the increase of rock bridge width, the dominant frequency band increases, while the normal stress increases, the average frequency decreases. This study can provide reference for the stability analysis of joint slope.

Key words: bridge, acoustic emission, direct shear tests, frequency spectrum analysis