Experimental Study On The Coupling Effect Of Stress And Gas Pressure

In this paper,the coupling effect of gassy coal stress and gas pressure is studied by laboratory test,theoretical deduction and numerical simulation.Based on the stress porosity response model and the porosity gas pressure response model,the coupling law of stress and gas pressure is obtained.The results show that the gas pressure with the loading stress increased and then decreased,according to the coal containing gas full stress-strain curve,when the volume strain to positive increases when the gas pressure increases with the stress,positive correlation between them;when the volume strain to the negative pressure of gas is increased,with increased stress there was a negative correlation between the two decreasing.The three axial compression test by confining stress strain curve and the physical and mechanical parameters of 2MPa,4MPa,6MPa pressure and initial gas pressure of 0.5MPa,1.0MPa,1.5MPa of the coal sample,according to the angle and Coulomb strength criterion is coal internal friction shear failure of coal containing gas is about 26 degrees angle.The elastic modulus,peak strain and peak volume strain of coal samples under different confining pressure and initial gas pressure are fitted,and the results show that it is a good linear relationship.By assuming physical parameters such as initial porosity,volume modulus,hydrostatic pressure and other physical parameters,stress and porosity response models were constructed to obtain stress and porosity response curves.The results show that the porosity of coal sample decreases with the increase of loading stress first and then increases,and the numerical simulation is carried out through RFPA,and the result is in accordance with the trend of stress porosity curve.According to the stress porosity model,the pore volume relation and the free gas content expression,the stress porosity gas pressure coupling model is set up,and the gas pressure coupling law of the gas coal stress is obtained with the porosity as the intermediate variable.Through the measurement of the mining stress and gas pressure of the coal seam,the gas pressure of the coal seam at the distance station 30m-40m reaches the peak value.Before the peak of the gas pressure,the gas pressure increases with the increase of the mining stress.After the peak of the gas pressure,the gas pressure decreases with the increase of the mining stress.