Research on the synthetic evaluation of the discontinuity in rocks

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The mechanical behavior of discontinuous rock masses in mainly determined by the properties of discontinuities, because the stiffness of discontinuities is greatly different from that of rock substances. Especially, the displacement is influenced by the configuration of discontinuity. Its configuration has usually an irregular surface.In this research, the surface configuration of rocks was measured as wave shape by the surface profiler and the frquency analysis was carried out on the obtained wave. The resulting power spectrum of the wave showed a characteristic curve against its frequency. It was found that the fractal dimension might be determined by this analysis on the surface configuration of rocks. Before and after a shearing test of the rock specimen with an artificial shear plane, the values of fractal dimension measured on the configuration of the shear plane were compared. It was found that the significant relationship between the fractal dimension and the strength exists in some rocks.On the other hand, the double-torsion test was carried out on several rocks. The fractal dimension was also examined on the crack surface developed by this test, regarding with the propagation velocity of crack. For these results, if the fractal dimension of the discontinuous planes can be measured, it seems to become a valuable index showing the mechanical properties of discontinuity in rocks.The scan-line method to evaluate the distribution of discontinuous planes in rock masses was developed and examined practically at some mines. The general formula for this evaluation was induced and the problems to use this method were considered. It was found that this method has a successful usage.