Abstract
This article presents the results for cyclic uni/triaxial tests on the deeply seated granite samples drilled from a −915 m deep tunnel in Sanshandao (SSD) gold mine. The monotonic and cyclic tests were carried out to observe the mechanical responses of the granite samples under different loading regimes. The disparities concerning the strain evolution and compressive strength of granite samples considering monotonic and cyclic uniaxial and triaxial loading are presented. Deformation behaviour, dissipated energy, and hysteresis are documented and evaluated. Quantitative correlations between strain evolution and cyclic stress levels are revealed. The amount of energy transformation during uniaxial and triaxial cyclic loading is determined. The impacts of confining pressure level on ultimate strain, energy dissipation, and stress‐strain phase shift are presented. The mechanical responses of the granite samples subjected to different stress paths and loading strategies are summarised, and corresponding interpretations are given to clarify the differences of mechanical behaviour encountered in distinct loading methods.
Highlights
Cyclic stress is extensively involved in civil engineering and mining procedures; the blasting, hydraulic fracturing, borehole drilling, and periodic excavations in underground space will give rise to chronic and intermittent vibrations, which are often associated with appearance of repeated loads [1, 2]
Considering the actual in situ stress pattern, corresponding cyclic tests were conducted in the laboratory and deformation behaviour, and energy balances and stress-strain phase shift are investigated using rock samples subjected to different axial stress levels and confinements
Our tests indicate a slight enhanced average compressive strength (152.5 MPa) when exposed to cyclic loading compared with triaxial monotonic loading
Summary
Cyclic stress is extensively involved in civil engineering and mining procedures; the blasting, hydraulic fracturing, borehole drilling, and periodic excavations in underground space will give rise to chronic and intermittent vibrations, which are often associated with appearance of repeated loads [1, 2]. Cyclic loading has direct impacts on the stability of surrounding rocks and can result in the sudden failure of the rock mass [3,4,5,6,7,8] Various mechanical properties, such as elastic modulus [9,10,11,12], shear modulus [13, 14], ultrasonic wave velocity [2, 15], and the material strength [16,17,18,19], are all found to be degraded with loading duration when exposed to the cyclic stress. The mechanical behaviours of the deeply buried brittle rocks subjected to the uni/triaxial stress state are of great significance to study and reveal the damage mechanism of deep hard rocks when the mining induced stress is considered, and the blasting and hydraulic fracturing can both obviously generate the seismic wave, which is accompanied by the cyclic stresses. Considering the actual in situ stress pattern, corresponding cyclic tests were conducted in the laboratory and deformation behaviour, and energy balances and stress-strain phase shift (hysteresis) are investigated using rock samples subjected to different axial stress levels and confinements
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