| The occurrence condition of coal seam gas is complicated in China, mainlyreflecting in low permeability. As a result, normal gas-drainage drilling can not workwell, and some other stress-relief and permeability-enhancement measures should betaken to enhance the drainage efficiency, among which, the drilling-slotting-integration technique is an effective and competitive one. Outburst-threat coalseams, however, are prone to be of high gas and low permeability, consequently thephenomenon of coal or gas spurt always occurs during drilling-slotting process,which, hinders the slotting progress, and to some extent, restricts the larger-scaleapplication of this slotting technique.Aiming for perfecting the slotting theory and equipment, providing guidancesfor coal-mine anti-spurt work and guaranteeing the safe effective slotting process, inthis thesis, I conduct research on coal or gas spurt by means of theoretical analysis,on-site investigation, numerical simulation, device and corresponding slottingprocess design and industrial test, etc. of which, outcomes are as follows:First of all, based on the theoretical accumulation and on-site experience, theintroduction to coal or gas spurt was developed: the concept of spurt was put forward,after which, I classified the spurt according to three different criteria, meanwhile,comparing with normal hole-spraying, main characteristics of spurt were discussed,and I also analyzed the advantages and disadvantages of spurt.Secondly, energetically speaking, the drilling outburst process was decribed bytaking advantage of the integrated effect hypothesis. Meanwhile, from the angle oftwo-phase flow of coal slurry and gas, the hydraulic deslagging flow patterns andtheir characteristic parameters in the circinate path were analyzed while the drill piperotates and not respectively. Based on above theories, I studied the spurt mechanismin phases of dry-type drilling and return-drilling slotting, which laid theoreticalfoundation for the further anti-spurt research.Thirdly, two kinds of slotting modes strong water and sharp cutting andfine water and blunt cutting were put forward according to different combinationsof drill rotation speed and slotting water pressure, after which, the effects of differentfactors (slotting mode, slotting phase and coal-seam thickness, etc.) on spurt werestudied respectively through using FLAC3Dnumerical simulation software andengineering practice. It could be found that by means of strong water and sharp cutting slotting, the spurt was more prone to occur. Finally outburst elimination andcontrollable spurt both taken into consideration,15MPa、160r/min were regarded asthe optimal water pressure and rotation speed.Finally, the new-type anti-spurt device having three functions of disposing coalslurry, extracting gas and dedusting was manufactured, at the same time, thecorresponding construction process was come up with, which adopted slow dry-typedrilling and fine water and blunt cutting slotting and therefore, was quite effectiveand practical. The industrial test results show that the novel device and itsapplication method perform extremely well in extracting gas and dedusting (theroadway gas concentration<0.2%, and the average dedusting efficiency>90%),which guarantees the safe and efficient slotting process and consequently enhancesthe effect of eliminating coal and gas outburst. |
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