Journal
ROCK MECHANICS AND ROCK ENGINEERING
Volume 49, Issue 10, Pages 3873-3886Publisher
SPRINGER WIEN
DOI: 10.1007/s00603-016-1077-y
Keywords
Uniaxial cyclic loading and unloading compression; Rock deformation and failure; Acoustic emission; Energy density; Energy evolution
Funding
- Fundamental Research Funds for the Central Universities [2015QNA62]
- National Natural Science Foundation of China [51504237]
- National Science Fund for Excellent Young Scholars of China [51322401]
- 973 National Basic Research Program [2015CB251601]
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Characteristics of energy accumulation, evolution, and dissipation in uniaxial cyclic loading and unloading compression of 30 sandstone rock specimens under six different loading rates were explored. Stress-strain relations and acoustic emission characteristics of the deformation and failure of rock specimens were analyzed. The densities and rates of stored energy, elastic energy, and dissipated energy under different loading rates were confirmed, and an effective approach for the equivalent energy surface was presented. The energy evolution of rock deformation and failure were revealed. It turns out that the rock deformation behavior under uniaxial cyclic loading and unloading compression remained almost unchanged compared with that of uniaxial compression. The degree of match between reloading stress-strain curves and previous unloading curves was high, thereby demonstrating the memory function of rock masses. The intensity of acoustic emission fluctuated continually during the entire cyclic process. Emissions significantly increased as the stress exceeded the unloading level. The peak of acoustic emission increased with increasing loading stress level. Relationships between energy density and axial load indicate that the rock mass possesses a certain energy storage limitation. The energy evolution of rock masses is closely related to the axial loading stress, rather than to the axial loading rate. With increasing axial loading stress, stored energy varied most rapidly, followed by that of the elastic energy, then dissipated energy. Energy accumulation dominates prior to the axial load reaching peak strength; thereafter, energy dissipation becomes dominant. The input energy causes the irreversible initiation and extension of microcracks in the rock body. Elastic energy release leads to sudden instability of rock bodies and drives rock damage.
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