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| DAMAGE EVOLUTION OF JOINTED ROCK MASSES UNDER UNIAXIAL COMPRESSION BASED ON DIGITAL IMAGE ANALYSIS |
| CHEN Xin，LU Wentao，SUN Jingya |
| (School of Mechanics and Civil Engineering，China University of Mining and Technology，Beijing 100083，China) |
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Abstract The digital images of the surface of jointed gypsum samples under uniaxial compression were analyzed in order to study the damage evolution of jointed rock mass quantitatively. A computing program was developed with Matlab for the identification of individual crack and the calculations of the length and orientation of cracks，the fractions of total crack area and the total fractal dimensions of cracks. The results of the digital images considering the inclination angles and continuity rates of joints were analyzed. Both the fractions of total crack area and the total fractal dimensions of cracks increased with the increasing of axial strain in similar tendency. The specimens were classified into two groups according to the orientation angles of joints. The specimens with angles of 0°，15°，75°and 90°were assigned in the first group(the main failure mode is axial splitting)，and the ones with angles of 30°，45°and 60°in the second group(the main failure mode is shear sliding). The fractions of total crack area and the total fractal dimensions of cracks of the first group are larger than those of the second group. When the continuity factors of joints were the same，the fractions of total crack area of the specimens with different orientation angles of joint were largely the same at the beginning of tests；while the curves of the fractions of total crack area vs. the orientation angles of joint were V-shaped at the peak load and at the end of test (the maximum and the minimum values were for specimens with the orientation angles of joint of 0°and 45°respectively). The anisotropic characteristic of surface cracks of the jointed specimens at the beginning of test or during the loading can be represented by the distribution of fractions of crack area along the crack orientations. The study showed that the anisotropic damage evolution of jointed specimens was efficiently captured with the method of image analysis.
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Received: 18 June 2013
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2014, Vol. 33 
