One-dimensional Simulation Tests On Permeation Instability Of Coal Seam Containing Gas

In order to study coal seam in instability mechanism of gas permeability, a set of test device was developed. The device comprises a coal chamber, simulation of roadway, coal sample compaction device, exposing device for coal, pressure measuring and gas injection system. Coal sample chamber and the simulation of tunnel have the same structure, made of seamless steel pipes, in the form of more assembled, length of each section is 0.5m, diameter is 199mm,they were connected by flanges; Using the ball as uncovering coal device, valve diameter is 40mm, coal sample compaction device adopting Jack pressure, loading capacity is 25 MPa, elongation of Jack is 500mm to ensure coal samples can get uniform compaction. Gas injection system is the high-pressure nitrogen cylinder. Gas pressure sensor sampling interval is lms, the maximum range is IMPa.Coal critical pressure gradient simulation tests were made, the method is:coal sample grain size is less than 5mm. Under the pressure of 15MPa compaction, density of coal samples is 1.14g/cm3 and porosity is 13.4%, longitudinal wave velocity is 799m/s, different gas injection pressure of uncovering coal tests, the measured critical pressure gradient is 2.19MPa/m. Test results show that The rationality of the conclusion that the coal seam has the critical pressure gradientA comparison of filter layer coal uncovering simulation tests was made. Coal particle size is less than 5mm,compacted by 15MPa, gas injection pressure is 0.4MPa,First do no filter layer exposing coal tests was done twice, the quality of coal samples are 72.06kg and 72.35kg separately, outburst the coal quality after exposing coal herniation are 51.11kg and 48.66kg, outburst coal quality accounted for the total mass ratio are 70.9% and 67.3%; in else same condition, installing sand before uncovering coal device as filter layer, quality of coal sample is 73.88kg, quality of exposing coal outburst is 4.76kg, outburst coal quality accounted for the total mass ratio is 6.4%. The experimental results show the rationality of the principle of the anti filter layer control process.