Abstract: The acoustic emission experiments on marble under the uniaxial compression are carried out. The fast Fourier transform is applied to obtain the two-dimensional spectrum of the acoustic emission signal, and the spectrum parameters such as dominant-frequency, secondary dominant-frequency are extracted. Then,??-value, i.e., the ratio of the dominant-frequency to secondary dominant-frequency, and ?-value, i.e., the ratio of the dominant-frequency amplitude to secondary dominant-frequency amplitude, are adopted to characterize the spectrum characteristics of acoustic emission signal. The fractal theory is also used to study the characteristics of acoustic emission spectrum during the rupture process of marble. The results show that (1) the secondary dominant-frequency characteristics of acoustic emission in marble fracture process are not the common phenomenon of all waveforms, but are unique to some signals. The acoustic emission signals can be classified into two types: class A signals have only dominant-frequency characteristics, class B signals have both dominant-frequency and secondary dominant-frequency characteristics. (2) From the rock crack growth to failure stage, the low value event rates of two types of signals (i.e., class A and class B) decrease and gradually disappear the increase rate of the cumulative number of events presents a significant increase. (3) Both the dominant-frequency band and the secondary dominant-frequency band of the acoustic emission signal have the similar distribution characteristics, showing a continuous and dense strip-like evolution feature. (4) Both the ??and ? have fractal characteristics. With the increase of rock damage, their correlation dimension declines to some extent.

Key words: marble, acoustic emission (AE), spectrum characteristics, dominant-frequency, secondary dominant-frequency, fractal