| Although there are many gas controls and measures for reductions in high gas, low permeability, medium-hard coal seam, high production and high efficiency coal face, there still exsiting problems of gas concentration exceeding limits and greater coal dusts during mechanized production period. Based on reviewing the coal seam water injection, hydraulic fracturing and hydraulic extrusion technique, the paper analyzed the difference between hydraulic pressing and the above hydraulic measures.Using rock mechanics, rock and fluid mechanics, gas flow and storage in coal seam, seepage coupling, elastic-plastic-damage mechanics, fracture mechanics and other theories, the paper researched coal body failure process of hydraulic pressing as well as the influence of high pressure water on gas desorption law, illustrated the mechanics of preventing gas and dust. On the basis of researching the basic parameters and technical parameters which influence the effect of hydraulic pressing, the paper obtained the most important order of technical parameters and the best parameter combination by adopting quantification theory to establish coal displacement prediction mathematical model and using orthogonal test. On the basis of seepage-stress coupling theory, the paper established seepage-stress-damage coupling model of coal body rupture process, reconstructing rupture and displacement process under high water pressure.by means of F-RFPA2D that can generate stress fields, acoustic emission fields and displacement fields in simulation. Through the hydraulic pressing experiments carried out in Qinan coalmine of Huaibei mining group,the paper showed the significant effect of gas extrusion and dust prevention. |
