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| Investigation on the correlation between mechanical characteristics and fracturing fractal dimension of rocks containing a hole and multi-flaws |
| ZHANG Ke1，2，LIU Xianghua1，LI Kun1，WU Wenyuan1 |
(1. Faculty of Electric Power Engineering，Kunming University of Science and Technology，Kunming，Yunnan 650500，China；
2. Faculty of Civil and Architectural Engineering，Kunming University of Science and Technology，Kunming，Yunnan 650500，China) |
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Abstract In order to study fracturing and fractal characteristics of rocks containing a hole and multi-flaws，model specimens containing a hole and multi-flaws were prepared and uniaxial compression tests were conducted. Failure process of rock specimens was numerically studied by RFPA2D. Formation mechanism of tensile cracks and the effect of different flaw inclinations on the compression strength were explained by constructing an overhanging beam and structural plane mechanical model. Box-counting dimension method was introduced to quantify new cracks geometric distribution of physical and numerical model specimens after failure，and its correlation with fracture characteristics was investigated. Satisfactory agreement between numerical and test results indicate that the failure modes in the specimen can be classified into two modes，namely cutting through the flaw(mode I) and sliding along the flaw(mode II). The rock bridge near the pre-hole is considered as an overhanging beam model，and the generation of tensile cracks around the hole appears to be produced by the maximum bending moment acting at the non-symmetrical part of the overhanging beam. The compression strength of the specimens is weakened by pre-flaws，which can be explained by the structural plane mechanical model. With increasing the flaw inclination，the compression strength of the specimens decreases first and then increases，while the weakening factor shows a crosscurrent. The fractal dimension of new cracks geometric distribution of rock samples after failure is closely related to fracture characteristics. Compared with mode II，the specimen failing in mode I has a greater compression strength，leading to a higher fractal dimension. The results of data fitting show a positive correlation between the compression strength and the fractal dimension.
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2018, Vol. 37 
