Abstract
To investigate the specimen shape effect on rockburst proneness of rock materials, a string of conventional and single-cycle loading-unloading uniaxial compression tests was performed with cylindrical and cuboid red sandstone specimens. Despite similar development paths on stress-strain curves for the specimens with two shapes, the cuboid specimens generally show a higher uniaxial compressive strength than the cylindrical specimens. The energy evolution laws inside the two shaped specimens were explored. The results show that the input energy density (IED), elastic energy density (EED), and dissipated energy density (DED) of the two shaped specimens increased in a quadratic relationship with the increment of unloading level. Moreover, the linear relationships between the EED, DED, and IED were further confirmed for two shaped specimens, which were defined as the linear energy storage and dissipation laws, respectively. The energy storage coefficients and energy dissipation coefficients (the slopes of the linear relationships between the EED, DED, and IED, respectively) are almost independent of the specimen shape. According to the linear energy storage and dissipation laws, the peak EED and peak DED of every specimen can be calculated accurately. Finally, combining the failure process of rock specimens recorded by a high-speed camera, the elastic energy index (WET), the residual elastic energy index (AEF), and the far-field ejection mass ratio (MF) of each specimen were adopted to assess the rockburst proneness of the red sandstone sampled in cylindrical and cuboid. The results show that cuboid specimens exhibited stronger rockburst proneness than cylindrical ones, which favorably agreed with the actual failure phenomena.
Highlights
With the underground engineering developing to the deeper crustal areas, rockburst phenomena appear with a growing trend which pose a vast risk to mining operations and result in production losses [1,2,3,4,5,6,7]
E uniaxial compressive strength (UCS) of the cylindrical and cuboid specimens in uniaxial compression (UC) and single-cycle loading-unloading uniaxial compression (SCLUC) tests is shown in Table 2 and Figure 4. e UCS of the cuboid specimens was higher than that of the cylindrical specimens in general and approximately 12 MPa higher on average
Zhao et al [27] carried out the UC tests with cuboid specimens and cylindrical specimens, and the result showed the UCS of the cuboid specimens was approximately 4 MPa higher than that of the cylindrical ones
Summary
With the underground engineering developing to the deeper crustal areas, rockburst phenomena appear with a growing trend which pose a vast risk to mining operations and result in production losses [1,2,3,4,5,6,7]. Some scholars analyzed the rockburst proneness of rock materials from an energy perspective, and many rockburst proneness criteria were proposed and developed. Introduced the strain energy storage index WET with the single-cycle loading-unloading uniaxial compression (SCLUC) test, which has been widely used to assess the rockburst proneness of rock materials [19,20,21,22,23]; Wang and. All of these rockburst proneness criteria were obtained with cylindrical specimens. In many cases, cuboid specimens were often used when investigating rock behavior under complex stress states such as biaxial and true triaxial
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