Abstract
Abstract. Dynamic collapses of deeply mined coal rocks are severe threats to miners; in order to predict collapses more accurately using electromagnetic radiation (EMR), we investigate the spatiotemporal multifractal characteristics and formation mechanism of EMR induced by underground coal mining. Coal rock in the burst-prone zone often exchanges materials (gas, water and coal) and energy with its environment and gradually transitions from its original stable equilibrium structure to a nonequilibrium dissipative structure with implicit spatiotemporal complexity or multifractal structures, resulting in temporal variation in multifractal EMR. The inherent law of EMR time series during damage evolution was analyzed by using time-varying multifractal theory. Results show that the time-varying multifractal characteristics of EMR are determined by damage evolution processes. Moreover, the dissipated energy caused by the damage evolutions, such as crack propagation, fractal sliding and shearing, can be regarded as the fingerprint of various EMR micro-mechanics. The dynamic spatiotemporal multifractal spectrum of EMR considers both spatial (multiple fractures) and temporal (dynamic evolution) characteristics of coal rocks and records the dynamic evolution processes of rock bursts. Thus, it can be used to evaluate the coal deformation and fracture process. The study is of significance for us to understand the EMR mechanism in detail and to increase the accuracy of the EMR method in forecasting dynamic disasters.
Highlights
With coal mining deepening, dynamic disasters such as rock burst and roof collapse become increasingly severe, threatening mine safety and efficient production
Based on real-time field monitoring data, in this paper, we analyze an electromagnetic radiation (EMR) multifractal spectrum to explore the mechanisms for EMR generation in the process of rock burst evolution, investigate the temporal response characteristics of EMR generated by coal rock burst during underground mining, reveal the nature of nonlinear, dynamical EMR changes, and further discuss the EMR multifractal practicability
EMR has an intrinsic relationship with the dissipated energy; from the point of view of thermodynamic laws and damage mechanics and based on the types of coal deformation and failure, we introduce the damage internal variable, construct a coal and rock dissipation potential function and establish the coupling model between EMR and dissipation energy, which reveals the nature of dynamic nonlinear characteristics of EMR
Summary
Dynamic disasters such as rock burst and roof collapse become increasingly severe, threatening mine safety and efficient production. As a natural, discrete medium, and sedimentary materials have many defects such as stratification, joints, pores, fractures, etc Dynamic disasters, such as rock burst and roof collapse, are instantaneous, instable phenomena occurring in coal rocks under the effects of external physical and chemical factors or stress. Based on real-time field monitoring data, in this paper, we analyze an EMR multifractal spectrum to explore the mechanisms for EMR generation in the process of rock burst evolution, investigate the temporal response characteristics of EMR generated by coal rock burst during underground mining, reveal the nature of nonlinear, dynamical EMR changes, and further discuss the EMR multifractal practicability.
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