Study on Rheological Properties of Coal Rock Containing Gas under Disturbance Conditions

Abstract

In view of the dynamic phenomenon that coal and rock are susceptible to external impact disturbance in the mining process, combined with the rheological hypothesis mechanism of coal and gas outburst, the RLSS-II-type triaxial loading creep test system of gas-containing coal and rock developed by ourselves is used to carry out the conventional triaxial rheological test of gas-containing coal and rock and the rheological disturbance effect test of gas-containing coal and rock under impact disturbance. The strength limit neighborhood of gas-containing coal and rock is determined, and the gas-containing coal and rock entering the strength limit neighborhood are subjected to different impact disturbances. The experimental results show that, (1) under the confining pressure of 0 MPa, 2.5 MPa, and 5 MPa, the longitudinal deformations of gas-bearing coal and rock are 32 mm, 27 mm, and 22 mm, respectively, indicating that the deformation of coal and rock will be affected by confining pressure, and with the increase of confining pressure, the deformation will decrease. (2) In the test, the deformation of coal and rock in the late stage of uniform creep stage can be regarded as a strain threshold. Before this threshold, the strain of coal and rock is not obvious, and the deformation is only 1.1 mm. After exceeding a threshold, the deformation of coal and rock is 9 mm, and the deformation increases significantly. Then, it enters the accelerated creep stage quickly and finally damages. The vicinity of this threshold is called the strength limit neighborhood of coal and rock containing gas. (3) The gas-bearing coal and rock without entering the strength limit neighborhood and entering the strength limit neighborhood are changed by confining pressure and different impact disturbance, respectively. It is found that, whether in the strength limit neighborhood or outside the strength limit neighborhood, the confining pressure has an effect on the strain, but the influence is not large. Under different impact disturbance, the deformation of coal and rock within and outside the strength limit neighborhood is 8 mm and 0.4 mm, respectively, and the deformation changes obviously, indicating that the impact disturbance has a great influence on the deformation of coal and rock within the strength limit neighborhood, and the coal and rock with large impact disturbance are destroyed before the coal and rock with small impact disturbance, indicating that the greater the impact disturbance, the shorter the time required for destruction.