| With the development of society and national economy, the construction of underground transport as well as the development and utilization of a variety of new energies have become one of the themes in present era. Rock fragmentation has also been involved into these areas, and its primary task is to ensure the security and efficiency of break rock and the stability of working space. Recently, the detection technique of electromagnetic emission(EME) has become a hot issue for researchers to study. It is very important for them to accurately predicate the degree of rock rupture and instability in the procedure of mechanical rock fragmentation. At the same time, they have to select a safe and effective equipment and manner. The EME characteristics of rock fragmentation under uniaxial load will be studied in this paper.Theoretical analysis and experimental test are used in the research. The main research contents and conclusions are as follows.(1) The theory of rock fragmentation and elastoplasticm mechanics are applied to analyze the stress distribution and rock breaking mechanism under the influence of indenter. And the evolution process, generating mechanism and influencing factors of EME in the procedure of rock fragmentation are discussed. The correspondence between EME signals and various stages of rock fracture are obtained, which provides theoretical foundation for experimental research and analysis.(2) The RMT-150 C rock mechanics test system, the KBD5 EME monitoring and data processing system are adopted to conduct an experiment on concrete and hard brittle granite fragmentation under uniaxial load. The results show that EME is produced by the fracture of concrete and granite, and EME signals gradually strengthen with the increase of loading rate. The differences exists in EME signals by using different types of indenter to break rocks. Cross indenter produces the strongest EME signals, followed by normal indenter, and the last one is spherical indenter.(3) A compared analysis between EME signals and acoustic emission(AE)signals is used to indicate their similarities as well as the differences between mechanism and evolution rules in the procedure of rock fracture. EME and AE have a respective corresponding relationship with the degree of rock deformation and fracture under load. That EME and AE technique are simultaneously applied to monitor the actual procedure of rock fracture has become more effectively.(4) The fractal rock mechanics theory is utilized to analyze the pulse signals of EME which is tested in the experiment. The fractal distribution characteristics of the EME pulse are distinctly presented in the broken procedure of experimental concreteand granite. Fractional dimension of EME turns into stronger with the increasing of loading rate, and it successively increases in spherical, normal and cross indenter. The size of fractional dimension can be adopted to predict the strength of EME pulse signals. |
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