Early-warning of rock burst in coal mine by low-frequency electromagnetic radiation

Abstract

Rock burst is one of the major geological hazards in coal mines and is difficult to prevent. Faced with this problem, the low-frequency electromagnetic radiation (EMR) test experiments of coal and rock were conducted to explore the characteristics of low-frequency EMR (1 kHz) signals induced form fractures. The relation between EMR signals and paroxysmal fractures was analyzed theoretically. Time-series extraction method was put forward to represent coal and rock paroxysmal fractures. The research results showed that deformation and fracture of coal and rock is caused by the accumulation of paroxysmal and discrete fractures in the samples. The time series obtained by moving average method shows rather good correlation with interior coal rock fractures, which has more obvious precursory characteristics of coal rock instability and dynamic disasters. When the coal rocks are damaged under uniaxial compression, low-frequency EMR (1 kHz) signals are more sensitive to local fracture with more abundant precursor information than high-frequency EMR (500 kHz) signals. The paroxysmal and discrete low-frequency EMR (1 kHz) signal is quite sensitive to rock burst, and when the signals representing coal rock fractures show an increasing trend and the high signals last for some time, it can be regarded as the precursor of rock burst disaster in coal mine. The separation technology of EMR representing coal rock fractures provided the key scientific basis for the field monitoring and forewarning of EMR technology, and a new method to identify the precursor of dynamic disasters of coal and rock.