Study on influence law of gas pressure on mechanical characteristic of coal samples in outburst coal seam

In order to study the influence of gas on mechanical parameters and dynamic disasters of coal and rock, the No.9 coal seam of No.2 well in Guiyuan Coal Mine was selected as the research object, the uniaxial compression test device of gas bearing coal and rock was designed, and the mechanical properties of coal and rock under different gas pressure were studied by using RMT-150C mechanical test machine. The results show that the gas pressure has a significant effect on the uniaxial compressive strength, stress-strain curve and elastic modulus of coal. The uniaxial compressive strength and elastic modulus of coal are negatively correlated with gas pressure; when the gas pressure is 0 MPa, 0.5 MPa, 1.0 MPa, 1.5 MPa and 2.0 MPa, the average compressive strength of the coal sample is 24.37 MPa, 19.37 MPa, 12.78 MPa, 10.40 MPa and 7.35 MPa, respectively, and the average elastic modulus is 3.388 GPa, 3.359 GPa, 2.614 GPa, 2.124 GPa and 1.143 GPa, respectively; compared with coal samples without gas, when the gas pressure is 0.5 MPa, 1.0 MPa, 1.5 MPa and 2.0 MPa, the uniaxial compressive strength of coal samples decreases by 20.52%, 47.56%, 57.32% and 69.84%, and the elastic modulus decreases by 0.86%, 22.85%, 37.31% and 66.26%, respectively. With the gradual increase of gas pressure, coal and rock change from brittleness to ductility, and the impact decreases gradually. The results are helpful to further reveal the internal causes of frequent coal and gas outburst accidents in Guizhou.