Evolution of Stress–Strain State in Structured Rock Specimens under Uniaxial Loading
V. N. OPARIN, O. M. USOL’TSEVA, V. N. SEMENOV, P. A. TSOI
N.A. Chinakal Institute of Mining, Siberian Branch, Russian Academy of Sciences, Krasnyi pr. 54, Novosibirsk, 630091б Russia
Keywords: rock mass, hierarchical block structure, laboratory experiment, speckle photography method, micro-strains, deformation-wave processes
Abstract
The comprehensive experimental studies into the change in the stress–strain state of rock specimens subjected to uniaxial loading until failure using automated digital speckle photography analysis shows that when stress reaches 50% of the limit strength of the specimens, low-frequency micro-deformation processes begin in the specimens under slow (quasi-static) stiff loading. Amplitude of the deformation-wave processes depends on the level of the pre-set macro-loading. Wave packets are plotted for averaged micro-strains obtained in sandstone and marble specimens under uniaxial compression. Fourier transforms are used to define amplitude–frequency characteristics of four micro-deformation stages: elastic, nonlinearly elastic, post-peak and residual strength regions. Elastic oscillations with frequency of 0.5–4 Hz appear at pre-failure stage and continue at post-peak loading stage.
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