Abstract
Rock joints have obvious acoustic emission (AE) Kaiser effect and Felicity effect under multilevel cyclic shear conditions. The TFD-20H/50J rock shear apparatus was used to carry out cyclic loading and unloading joint shear tests, and the acoustic emission parameters and frequency spectrum characteristics of the whole shearing process were analyzed. The results show that, under the cyclic loading, the shear stress-displacement curve forms several cyclic hysteresis loops, and the number of loops increases with the increase of normal stress. With the cycles increase, the shear damage gradually increases, and the Felicity ratio gradually decreases. The Felicity ratio at the final shear failure moment is about 0.94~0.99. The ratio of the RA value (rise time/amplitude) and the average frequency value (RA-AF) is used to classify the cracking mode of the joint sample. There are two AE crack signal types (tensile type and shear type) during shear damage. The peak frequency is displayed as high, medium, and low three frequency bands, which are distributed in the range of 0~35 kHz, 35~122 kHz, and 122~300 kHz, respectively. Both low-frequency and high-frequency signals account for less than 10%, and medium-frequency signals account for more than 90%. The research of the AE monitoring signals of multilevel shear behaviors can help understand the shear-friction mechanisms of rock joints.
Highlights
The deformation failure mechanism and slope instability mechanism of mine rock slopes in alpine area have always been the focus of mine disaster prevention research
Such advanced or delayed memory properties are usually estimated by Felicity ratio (FR value) [11,12,13], Geofluids which is the ratio of the stress with generating obvious acoustic emission activity to the previous peak stress, as shown in equation (1)
By processing and analyzing the acoustic emission (AE) signal, the shear failure behaviors of rock joints under different normal stress were studied from the point of view of tensile and shear crack signals, and the following four conclusions are obtained
Summary
The deformation failure mechanism and slope instability mechanism of mine rock slopes in alpine area have always been the focus of mine disaster prevention research. In the laboratory research of cyclic loading and unloading experiments, Kaiser first discovered the acoustic emission stress memory function of polycrystalline metal in 1950 [4, 5] and Goodman [6] proved that the rock has the Kaiser effect during loading. The Kaiser effect often appears at a stress level not exactly equal, but a little higher or lower than the previous largest stress of load. Such advanced or delayed memory properties are usually estimated by Felicity ratio (FR value) [11,12,13], Geofluids which is the ratio of the stress with generating obvious acoustic emission activity to the previous peak stress, as shown in equation (1)
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