Study On Infrared Radiation Temperature Characteristics And Surface Computational Stress Field Of Gassy Coal Damage

With the gradual entry of coal mine into deep mining,the combined effect of in-situ stress and gas pressure on coal body is more obvious.Under the condition of gas participation,the failure characteristics of coal body are different from those of coal without gas.Therefore,it is of great theoretical and practical significance to study the infrared radiation characteristics and damage evolution mechanism of coal and rock damage and failure process under the combined action of gas stress.In order to study the infrared radiation characteristics and damage evolution mechanism of gassy coal damage,we independently developed the stress-gas coupling damage infrared experimental system.We use this experimental system to carry out uniaxial compression infrared radiation experiment on gassy coal,and analyze the variation of infrared radiation temperature with gas pressure during the damage process of gassy coal,and study the fractal and multifractal characteristics of gassy coal damage infrared radiation temperature.According to the damage mechanics theory,we established the damage evolution model of gassy coal based on infrared radiation temperature,and studied the damage evolution characteristics of gassy coal,and deduced the mathematical method of coal surface calculate stress based on infrared radiation temperature,and studied the correlation between infrared thermal image of gassy coal damage and crack development and surface computational stress field.The specific research results are as follows:The maximum infrared radiation temperature will change during the damage process of coal containing gas,and the maximum infrared radiation temperature curve has stages.The existence of gas can reduce the accumulation rate of coal sample energy and the release rate of strain energy.With the increase of gas pressure,the strain energy of coal sample decreases gradually.The cumulative measurement of maximum infrared radiation temperature and strain energy of gassy coal are in good agreement with the exponential function of y=a*exp(-x/b).Infrared radiation temperature signals produced by gas-bearing coal rupture have obvious classification and multifractal characteristics.Hurst exponent of infrared radiation temperature of gas-bearing coal is greater than 0.5 in each damage period,and the infrared radiation temperature is positively correlated with time.The average Hurst exponent of infrared radiation temperature decreases with the increase of gas pressure,and the fractal dimension D is between 1.0 and 1.5.The multi-fractal spectrum of infrared radiation temperature signals can well reflect the process of gas-bearing coal rupture in different time periods,which changes from left hook to right hook.Especially,when the coal is destroyed,the right hook appears obviously.According to damage mechanics theory,a damage evolution model of gassy coal based on infrared radiation temperature is established.The damage-strain curve,which based on infrared radiation temperature,and the stress-strain curve of gassy coal have a high correlation before the instability and failure of coal body,and the damage-strain curve can well reflect the stress-strain process of coal body.The damage-strain curves of coal under different gas pressures show a sharp acceleration phenomenon in the damage stage,and the correlation between calculated stress and measured stress of gassy coal is more than 0.7,that showing a significant correlation,indicating that the calculated stress can well reflect the measured stress in the gassy coal damage process.Based on the infrared radiation temperature-containing gas damage evolution model,we derive a mathematical formula for calculating the surface computational stress field of coal based on infrared radiation temperature.Through the analysis of stress field nephogram and crack development picture of calculating surface of gassy coal,we find that the development process of high calculating surface stress area has a good correspondence with the coal body damage process.In the plastic phase and the post-stress peak failure stage,the high temperature point,high temperature band and high temperature area appear on the infrared thermal image and infrared difference cloud image of gassy coal,which has a good correspondence with the development of coal body fissure and the distribution state of surface computational stress field and high stress area.