Similar Simulation Test Of Coal And Gas Outburst Induced By Rock Cross-cut Coal Uncovering

In the process of underground coal mining,due to the complexity of the conditions of deep coal resources,coal and gas outbursts occur from time to time.In most outburst accidents,outbursts induced by rock cross-cut coal uncovering are the most typical and have the highest probability of occurrence,and intensity is the highest.The common method used to study mechanism of outburst induced by rock cross-cut coal uncovering is similarity simulation experiment,but existing devices used for similarity simulation experiment are not perfect in some aspects,resulting in a low degree of similarity.Therefore,development of a experimental device that takes into account the aspects,through outburst experiment to study evolution characteristics of many parameters in process of rock cross-cut coal uncovering,is of great significance to study mechanism of outburst.Based on the hypothesis of combined action of outburst,this paper put forward basic requirements of outburst experimental device,analyzed application of multi-functional physical model testing system in outburst experiments,and carried out similar simulation test,numerical simulation software was used to simulate process of rock cross-cut coal uncovering and evolution characteristics of various parameters were analyzed.The following conclusions are drawn:(1)Multi-functional physical model testing system consists of six parts.It has following characteristics,system has high rigidity and strong bearing capacity,it can simulate various geological structures,gas storage space is large,and system can achieve three-way independent loading,and can simulated excavation.(2)The experiment of outburst in rock cross-cut coal uncovering was carried out.Temperature,gas pressure,solid pressure and acoustic emission data were analyzed.In experimental vacuum stage,temperature in cavity will drop by about 4 ° C.After initial gas injection,coal absorbs gas,and temperature of coal will rise sharply.After gas injection again,temperature will increase slightly and show multiple peaks,but overall trend is declining.During excavation stage,temperature of coal in the cavity did not fluctuate significantly.Drill pipe was advanced in the rock,rock near coal was not damaged,gas did not escape from excavation opening,air pressure was at a stable value,and in-situ stress increased significantly,elastic potential energy in coal was accumulated,providing an energy basis for occurrence of outbursts.When outburst occurred,coal and gas shot out from outburst channel in a pulsed manner.Air pressure in the cavity dropped to atmospheric pressure in a short time.After destruction of surrounding rock,coal and gas was thrown out,stress value plummeted,and the acoustic emission count increased.(3)FLAC3D was used to carry out similar simulation experiments,and the evolution characteristics of in-situ stress,displacement and plastic failure zone were analyzed.Affected by excavation activities,stress will be redistributed,and a stress arch will be generated on the roof,and plastic damage areas will be generated on both roof and floor and roadway,displacement will occur towards goaf,roof will sink and floor will swell,a higher abutment pressure will be generated in front of working face,as working face advances,stress arch will expand and the abutment pressure will moves forward.When coal seam is exposed,abutment pressure in front of working face will transition from rock layer to coal seam,destroying coal body with lower strength.The elastic potential energy accumulated in coal in front of working face will be released,pressure will be quickly released,and displacement to goaf will suddenly increase.The destruction will intensify and extend into the coal seam,that is,outburst occurs.