Research on the device and method for measuring the initial velocity of in-situ gas emission from coal

The initial velocity of gas emission is one of the important indicators for identifying the risk of coal and gas outburst. The existing research has not organically combined the testing of the initial gas emission rate index of coal with the testing of the other three indicators for outburst identification (coal seam gas pressure, coal failure type, and coal solidity coefficient). The current method for measuring the initial velocity of gas emission is based on AQ 1080-2009 "Method for Measuring the Initial Velocity Index (∆p) of Coal Gas Emission". The measurement results only reflect the difficulty of gas emission through coal particles under standard experimental conditions, without considering the in-situ environment of coal seam gas occurrence. The results cannot accurately reflect the severity of the disaster of gas emission inside the coal rock mass on site. In order to solve the above problems, the device and method for measuring the initial velocity of in-situ gas emission are proposed. The method replaces coal particles with original coal blocks, replaces methane with original gas components, increases the gas pressure, stress, and temperature environment in which the coal body is located. The method restores the in-situ environment for measurement. A in-situ gas emission initial velocity measurement experiment is conducted by use of coal samples from coal and gas outburst coal seams in a certain coal mine. The conclusions are listed as follows. ① With the simulation of gas emission process, the gas emission flow rate gradually decreases and shows a negative exponential change law with time. The gas flow rate is used to characterize the initial velocity of in-situ gas emission, then Δp_QA=7.1 mmHg, Δp_QI=2.9 mmHg. ② As the simulation of the gas emission process progresses, the gas pressure in the emission space gradually increases, and the rate of gas pressure increase gradually decreases. The gas pressure changes roughly with time in a logarithmic function relationship. The emission gas pressure is used to characterize the initial velocity of in-situ gas emission, then Δp_PA=25 mmHg, Δp_PI=26.6 mmHg, Δp_PD=11 mmHg. The measurement results can comprehensively reflect the dual pore structure of coal seams, the mechanical properties of coal bodies, the energy of gas occurrence in coal bodies, the in-situ environment of stress and temperature in coal seams, and truly reflect the degree of outburst danger in coal mines underground.