Stress-charge-temperature coupling model of composite coal-rock in deformation and fracture

To explore the relationship between the mechanical properties of composite coal-rock and charges, temperature signals, the roof slate, coal sample and floor rock were extracted from the Datong Xinzhouyao mine with the typical coal-rock dynamic fault characteristics of coal seam.The coal-rock samples consist of roof rock, coal seam and floor rock in proportion of 1:1:1.The uniaxial compression experimental investigation was conducted in three different loading rates of 0.1, 0.3 and 1.0 mm/min respectively.This paper discusses the variation law of electromagnetic emission (EME), charge and temperature during the process of coal-rock uniaxial loading deformation and fracture.The experimental results demonstrate there are obvious precursor signals of in-duced-charges, electromagnetic emission pulse and temperature before the rupture of the unstable coal-rock.The EME and induced-charges signals are weak at the initial stage of loading.Both signal strengths gradually increase with the increase of loading stress, and reach the strongest values before the peak stress.Both signals have strong consistency.There is a quadratic polynomial relationship between the EME and charge-induced, and the multiple correlation coefficient is above 0.8.Compared with the variation characteristics of the EME signal, the duration of the charge-induced signal is shorter and the signal characteristics are paroxysmal.When the loading rate is 0.1 mm/min, the induced-charges signal is the strongest, at 0.3 and 1.0 mm/min.The loading rate is higher and the change rate of induced-charges become greater.The temperature presents an increasing tendency of step type, and reaches the maximum before the stress peak.Based on the SET (stress-electricity-thermal) coupling model, the mathematical relationship between the EME pulses and the charge-induced voltage was derived.The SCT (stress-charge-thermal) coupling model was built.According to the test of 12 sets of samples, the data fitting results show that the experimental data fit the SCT coupling model parameters n, b', the multiple correlation coefficients are all above 0.9.Its accuracy is slightly higher than the SET coupling model parameters m, b.The EME, induced-charges signals and temperature produced by composite coal-rock are connected with free charge, internal fracture, friction and other factors.In the coal mine, the signal disturbance degree of induced-charges is smaller than the EME.Therefore, the SCT coupling model could be considered to predict and prevent the coal-rock dy-namic disaster. © 2019, Editorial Office of Journal of China Coal Society. All right reserved.