Abstract
Abstract Computed tomography (CT) scanning technology is helpful in investigating rock materials as it can demonstrate the micro structure of rock clearly. Conventional triaxial compression tests and the corresponding graded triaxial loading tests were carried out to investigate the complex failure mechanism of the marble at the Jinping Hydropower Station. After that CT-scanning tests were done on the loaded marble specimens. The test results show that (1) the CT numbers of the specimens have a certain statistical regularity, that is, the CT numbers of the specimens under different confining pressures satisfy the Weibull distribution, as the confining pressure increases, the mean values rise while variances decrease; (2) in the two groups of tests, the average CT numbers corresponding to the conventional triaxial tests are higher than those corresponding to the graded loading tests, but the CT number variances are lower than those of the graded loading tests; and (3) according to meso-damage mechanics, the damage variables of the rock specimens were established based on the definition of CT numbers. The calculation results show that the damage variables decrease with the increase in confining pressure, the damage variables of the rock specimens in the graded loading tests are higher than those in the conventional triaxial test, and the differences between the two loading tests have grown with the increase in confining pressure.
Highlights
With the development of science and technology, more advanced scientific and technological methods have been applied in studying rock materials
Yang et al found that the computed tomography (CT) number is closely related to rock damage, and defined the damage variable based on the CT number [3]
Li et al conducted a CT-scan test on the rock under cyclic loading and found that the CT number and its standard deviation can reflect the distribution of rock cracks [5]
Summary
With the development of science and technology, more advanced scientific and technological methods have been applied in studying rock materials. In this study, based on the CT-scan data of damaged rock samples, combined with the theory and technology of digital image processing, the variation law of the CT number of marble samples under different loading paths was analyzed. The conventional triaxial compression tests and the corresponding graded loading tests under different confining pressures were conducted systematically. The graded loading triaxial compression tests were carried out according to the peak strength (σc) obtained from the conventional triaxial compression tests under different confining pressures. Under the same confining pressure, the axial stress in the graded loading triaxial compression test was loaded to 60% of the peak strength in the conventional triaxial tests successively, and maintained for 48 h. This strength grade, the rock sample has entered the crack initiation stage
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