Characterization And Mechanism Of Infrared Radiation Response During Instability Damage Of Loaded Coal Rocks

Coal and gas prominence,impact pressure,and other coal-rock dynamic disasters are particularly evident in all types of coal mine disasters.Coal-rock dynamic disasters are a complex physical phenomenon,and their characteristics and measurable physical quantities are multi-scale,multi-level,and multi-modal,and are accompanied by acoustic,electrical,optical and magnetic radiation information in the process of destabilization.This paper investigates the characteristics and laws of infrared radiation response during the destabilization of loaded coal rocks under different factors,and clarifies the mechanism of infrared radiation generation,to provide a theoretical basis for monitoring the stability of coal rocks and early warning of coal rock dynamic disasters by using infrared thermal radiation technology.In this paper,the physical and mechanical properties of the coal rock specimens and the infrared radiation during the destabilization damage were tested using a gas-bearing coal rock rupture temperature variation detection experiment system,and the characteristics and patterns of infrared radiation response under different factors（such as loading rate,moisture,damage degree and gas pressure）were investigated in-depth and systematically using the techniques of extracting the characteristic information in the time domain and spatial distribution.The results show that the infrared radiation response of coal rocks under different factors（e.g.loading rate,moisture,damage,and gas pressure）can be measured.The results show that the IR radiation of coal rocks exhibits different spatial and temporal evolution characteristics under different factors;the faster the loading rate of the specimen,the earlier the moment of appearance of the thermal image anomaly;moisture increases the IR radiation intensity of the specimen,but also suppresses the change of IR radiation volatility;gas pressure affects the IR radiation temperature precursor characteristics of the specimen before rupture,and the appearance of anomalous bands and areas during the loading process and the moment of rupture The Euclidean distanceΔT_d precursors of specimens with different degrees of damage appear earliest,followed by the temperature coefficient of variation Tcv,and the differential maximum temperatureΔT_MIR is the latest,and the precursor time difference based on different parameters is helpful to enhance the reliability of early warning identification and determination of coal-rock dynamic catastrophes.Based on the experimental analysis and multi-field coupling theory,a coupled heat-flow-solid equation that can represent the temperature change of the loaded coal rock is constructed,and the COMSOL numerical simulation software is applied to numerically simulate the surface temperature change during the loaded damage of the coal body under different factors（gas pressure,moisture and elastic mode,etc.）,and the reliability of the numerical simulation is verified by comparison with the experimental results in the previous paper.Finally,using the numerical simulation and experimental results,the regression analysis of the influence of different factors on the surface temperature variation of the coal body was carried out,and the influence of stress on the surface temperature variation of the coal body was significant.Using PFC2D particle flow discretization software,combined with the experimental results of coal samples with different degrees of damage,the numerical simulation analyzed the crack development and expansion evolution law during the damage by loaded samples.The results show that the greater the strength of the specimen,the greater the damage after destruction;the damage morphology of the numerical simulation is consistent with the experimental damage morphology and the distribution of infrared thermal image anomalies;the development and expansion of different fractures（shear fracture and tensile fracture）result in the difference of the surface temperature of the coal body,and the microfracture development and expansion inevitably cause the response of infrared radiation.Based on the thermal coupling theory,the frictional heat of microfracture,and the thermal effect of the gas desorption process,it is revealed that there are four main thermal effects in the process of loaded instability of coal rocks,namely,the thermoelastic effect,the frictional heat effect,the thermal effect of gas expansion and the thermal effect of gas desorption.On this basis,the influence of loading rate,moisture,coal body strength,and gas pressure on the infrared radiation of coal rocks is analyzed and studied.In-depth research on the characteristics and laws of infrared radiation response of loaded coal rocks under different factors deepens and improves the mechanism of infrared radiation generation from coal rocks,which is of great theoretical significance and application value for further revealing the evolution mechanism of coal rock dynamic disasters,monitoring the stability of coal rocks and early warning of coal rock dynamic disasters by using infrared thermal radiation technology.The paper has 84 figures,11 tables and 151 references.