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Post-peak Stress–Strain Curves of Brittle Rocks Under Axial- and Lateral-Strain-Controlled Loadings
https://orcid.org/0000-0002-7403-3206
Abstract To systematically study the influence of axial- and lateral-strain-controlled loadings on the strength and post-peak deformation behaviors of brittle rocks, four types of rocks (marble, sandstone, granite, and basalt) are tested under uniaxial and triaxial compressions, using a brittle hard rock testing system named Stiffman with high loading system stiffness. The test results show that the post-peak stress–strain curves of rock specimens under axial-strain-controlled loading are Class I, while those under lateral-strain-controlled loading are mostly Class II when the confining pressure is low. As confining pressure increases, the stress–strain curves change to Class I. Compared with that under lateral-strain-controlled loading, the failure of rock under axial-strain-controlled loading is more intense, the peak strength is higher, and the residual strength is lower. It is demonstrated that Class II post-peak stress–strain curves obtained by lateral-strain-controlled loading are caused by the unloading of the actuator in response to the servo-control system to keep the lateral strain rate constant. In the post-peak deformation stage, large dilation occurs, which leads to a sudden increase of the lateral strain rate; in order to keep the lateral strain rate at the set value under lateral-strain-controlled loading, the servo-control system must force the actuator to unload. When rock dilation occurs in the pre-peak deformation stage, unloading can occur before the peak strength, resulting in a decrease of peak strength compared with the peak strength obtained by axial-strain-controlled loading. It is found that the more brittle and dilatant a rock, the earlier the unloading of the actuator is, and the larger the peak strength decreases and the more obvious the Class II curve is.
Post-peak Stress–Strain Curves of Brittle Rocks Under Axial- and Lateral-Strain-Controlled Loadings
https://orcid.org/0000-0002-7403-3206
Abstract To systematically study the influence of axial- and lateral-strain-controlled loadings on the strength and post-peak deformation behaviors of brittle rocks, four types of rocks (marble, sandstone, granite, and basalt) are tested under uniaxial and triaxial compressions, using a brittle hard rock testing system named Stiffman with high loading system stiffness. The test results show that the post-peak stress–strain curves of rock specimens under axial-strain-controlled loading are Class I, while those under lateral-strain-controlled loading are mostly Class II when the confining pressure is low. As confining pressure increases, the stress–strain curves change to Class I. Compared with that under lateral-strain-controlled loading, the failure of rock under axial-strain-controlled loading is more intense, the peak strength is higher, and the residual strength is lower. It is demonstrated that Class II post-peak stress–strain curves obtained by lateral-strain-controlled loading are caused by the unloading of the actuator in response to the servo-control system to keep the lateral strain rate constant. In the post-peak deformation stage, large dilation occurs, which leads to a sudden increase of the lateral strain rate; in order to keep the lateral strain rate at the set value under lateral-strain-controlled loading, the servo-control system must force the actuator to unload. When rock dilation occurs in the pre-peak deformation stage, unloading can occur before the peak strength, resulting in a decrease of peak strength compared with the peak strength obtained by axial-strain-controlled loading. It is found that the more brittle and dilatant a rock, the earlier the unloading of the actuator is, and the larger the peak strength decreases and the more obvious the Class II curve is.
Post-peak Stress–Strain Curves of Brittle Rocks Under Axial- and Lateral-Strain-Controlled Loadings
https://orcid.org/0000-0002-7403-3206
Abstract To systematically study the influence of axial- and lateral-strain-controlled loadings on the strength and post-peak deformation behaviors of brittle rocks, four types of rocks (marble, sandstone, granite, and basalt) are tested under uniaxial and triaxial compressions, using a brittle hard rock testing system named Stiffman with high loading system stiffness. The test results show that the post-peak stress–strain curves of rock specimens under axial-strain-controlled loading are Class I, while those under lateral-strain-controlled loading are mostly Class II when the confining pressure is low. As confining pressure increases, the stress–strain curves change to Class I. Compared with that under lateral-strain-controlled loading, the failure of rock under axial-strain-controlled loading is more intense, the peak strength is higher, and the residual strength is lower. It is demonstrated that Class II post-peak stress–strain curves obtained by lateral-strain-controlled loading are caused by the unloading of the actuator in response to the servo-control system to keep the lateral strain rate constant. In the post-peak deformation stage, large dilation occurs, which leads to a sudden increase of the lateral strain rate; in order to keep the lateral strain rate at the set value under lateral-strain-controlled loading, the servo-control system must force the actuator to unload. When rock dilation occurs in the pre-peak deformation stage, unloading can occur before the peak strength, resulting in a decrease of peak strength compared with the peak strength obtained by axial-strain-controlled loading. It is found that the more brittle and dilatant a rock, the earlier the unloading of the actuator is, and the larger the peak strength decreases and the more obvious the Class II curve is.
Post-peak Stress–Strain Curves of Brittle Rocks Under Axial- and Lateral-Strain-Controlled Loadings
Hou, P. Y. (author) / Cai, M. (author) / Zhang, X. W. (author) / Feng, X. T. (author)
2021
Article (Journal)
Electronic Resource
English
BKL:
38.58
Geomechanik
/
56.20
Ingenieurgeologie, Bodenmechanik
/
38.58$jGeomechanik
/
56.20$jIngenieurgeologie$jBodenmechanik
RVK:
ELIB41
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