Journal
JOURNAL OF ROCK MECHANICS AND GEOTECHNICAL ENGINEERING
Volume 12, Issue 6, Pages 1249-1262Publisher
SCIENCE PRESS
DOI: 10.1016/j.jrmge.2020.08.002
Keywords
Fatigue loading; Confining stress unloading; Unloading rate; Energy evolution; Computed tomography (CT) scanning
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Funding
- National Key Technologies Research & Development Program [2018YFC0808402]
- State Key Laboratory for GeoMechanics and Deep Underground Engineering, China University of Mining and Technology [SKLGDUEK1824]
- Fundamental Research Funds for the Central Universities [FRF-TP-20-004A2]
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Rocks in underground works usually experience rather complex stress disturbance. For this, their fracture mechanism is significantly different from rocks subjected to conventional triaxial compression conditions. The effects of stress disturbances on rock geomechanical behaviors under fatigue loading conditions and triaxial unloading conditions have been reported in previous studies. However, little is known about the dependence of the unloading rate on fatigue loading and confining stress unloading (FL-CSU) conditions that influence rock failure. In this paper, we aimed at investigating the fracture behaviors of marble under FL-CSU conditions using the post-test X-ray computed tomography (CT) scanning technique and the GCTS RTR 2000 rock mechanics system. Results show that damage accumulation at the fatigue stage can influence the final fracture behaviors of marble. The stored elastic energy for rock samples under FL-CSU tests is relatively larger compared to those under conventional triaxial tests, and the dissipated energy used to drive damage evolution and crack propagation is larger for FL-CSU tests. In FL-CSU tests, as the unloading rate increases, the dissipated energy grows and elastic energy reduces. CT scanning after the test reveals the impacts of the unloading rate on the crack pattern and a fracture degree index is therein defined in this context to represent the crack dimension. It shows that the crack pattern after FL-CSU tests depends on the unloading rate, and the fracture degree is in agreement with the analysis of both the energy dissipation and the amount of energy released. The effect of unloading rate on fracture evolution characteristics of marble is revealed by a series of FL-CSU tests. (C) 2020 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V.
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