Abstract
Rockburst is a highly destructive geological disaster caused by excavation and unloading of hard and brittle rock mass under high geostress environment. Quantitative evaluation of rock brittleness and rockburst proneness is one of the important tasks in potential rockburst assessment. In this study, uniaxial compression and acoustic emission tests were carried out for basalt, granite, and marble, and their brittleness and rockburst proneness were quantitatively evaluated. The acoustic emission evolution characteristics of the three rocks during uniaxial compression were analyzed, and the differences of fracture mechanism of the three rocks were compared. The results show that (1) based on the brittleness evaluation index, basalt is the most brittle rock, followed by granite, and marble is the weakest; (2) based on the rockburst proneness evaluation index, combined with the macroscopic failure phenomenon and morphology of the samples, the rockburst proneness of basalt is the strongest, followed by granite, and marble is the weakest; (3) there exists a positive correlation between rockburst proneness and brittleness, and the fitting results show that they are approximately exponential; and (4) brittleness has an important influence on the rock fracture mechanism. Unlike marble, basalt and granite with strong brittleness continuously present high-energy acoustic emission signals in the stage of unstable crack propagation, and large-scale fracture events continue to occur; from the calculation results of the acoustic emission b value, the stronger the brittleness of rock, the larger the proportion of large-scale fracture events in the failure process.
Highlights
As the representative of dynamic disasters under high stress conditions [1,2,3,4,5,6], rockburst makes rock mechanics researchers gradually realize the importance of revealing the brittle failure mechanism of rock for engineering safety
acoustic emission (AE) characteristics of Beishan granite under conventional triaxial compression (CTC) and hydromechanical (HM) coupling tests are conducted by Zhou et al [20], and the results show that AE events proportion at the same loading period changes under different confining pressures, which illustrates that the failure pattern develops from splitting to ductile shearing failure with the increasing confining pressure
The calculation of Wcf is more complicated because of the need of integral calculation based on the stress-strain curve. e index Es can be calculated by uniaxial compressive strength and elastic modulus. erefore, the index Es was taken to analyze the rockburst proneness of three kinds of rocks. e calculation results are listed in Table 1, which show that the index Es of basalt, granite, and marble is 0.507, 0.357, and 0.164, respectively. e rockburst proneness of basalt, granite, and marble belongs to the range of moderate rockburst, weak rockburst, and no rockburst, respectively
Summary
As the representative of dynamic disasters under high stress conditions [1,2,3,4,5,6], rockburst makes rock mechanics researchers gradually realize the importance of revealing the brittle failure mechanism of rock for engineering safety. Li et al [11] summarized twenty basic brittleness evaluation methods and established a comprehensive brittleness evaluation index based on the stress-strain curve. Ai et al [13] defined brittleness as the ability of a rock to accumulate elastic energy during the prepeak stage and to self-sustain fracture propagation in the postpeak stage and proposed. Xia et al [14] proposed a brittleness index based on the postpeak stress drop rate of the stress-strain curve and the ratio of elastic energy released during instability failure to total energy stored before peak strength. Chen et al [15] comprehensively considered the postpeak stress-drop rate and the stress growth rate between the crack initiation stress and Advances in Civil Engineering the peak stress and established a brittleness index calculation method based on the whole stress-strain curve
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