Development and application of multi-functional test system for coal and gas outburst simulation

A multi-functional test system for coal and gas outburst simulation, composed of specimen cavity, loading module, seepage module, outburst inducing module, roadway module and data acquisition module, was independently developed based on modular development idea. The size of specimen cavity is φ200 mm×700 mm, and its sealing gas pressure and axial loading stress are respectively 10.0 MPa and 20.0 MPa. The size and light transmittance of the roadway are φ200 mm×10 m and 94%, respectively. The diameter of the outburst mouth is optional with 25 mm, 50 mm and 100 mm. The test system can realize the functions of one time forming of coal samples, permeability test of coal samples and visualization of coal-gas two-phase flow. Taking Longshan Coal Mine in Henan Province as the engineering background, the outburst simulation test was carried out, and the results show that: (1) the permeability of the coal specimen is 9.88×10-3μm2, and the outburst inducing process reaches the millisecond level. After the outburst is trigger, the pulverized coals entrained by high-pressure gas continue to be thrown into the roadway to form a coal-gas two-phase flow. The outburst pulverized coal is 9540.0 g, and the relative outburst strength is 47.7%.(2) During the outburst process, the roadway air is compressed to produce multiple shock waves that gradually attenuate in the form of alternating positive pressure and negative pressure, and the peak value of the shock wave overpressure reaches a maximum of 15.41 kPa at 5.5 m in the middle of the roadway. At the same time, the backward moving rarefaction wave generates to make the coal seam pressure in the cavity increase by 21%.(3) The outburst pulverized coal flow has the multiple reacceleration processes due to the paroxysmal outburst characteristics and the gas desorption, reaching the peak velocity of 42.6 m/s after the second acceleration. The shock wave propagates in the roadway ahead of the coal-gas two-phase flow at supersonic speed, and the wave front velocity is as high as 361.76 m/s which is much higher than that of the pulverized coal flow. (4) The two-phase flow temperature is mainly controlled by the endothermic process of the gas desorption and the disturbance of the shock wave, showing an evolutionary trend of "short rise, rapid decline and slow recovery". The closer to the outburst mouth, the greater the decline of the temperature, with a maximum decrease of 2.1 ℃. The farther away from the outburst mouth, the greater the rise, and the maximum rise is 0.6 ℃. It is shown that the test system is stable and reliable, and can accurately measure the permeability of the specimen, realistically simulate the whole process of outburst, which provides an effective means for in-depth study of outburst disaster causing mechanism and guiding outburst prevention and control in coal mines. © 2022, Science Press. All right reserved.