Advantageous Channel Evolution Mechanism And Application Of Pressure Relief Gas Storage And Transportation In Gently Inclined Coal Seam

At the present stage,coal is China's main energy,and it has greatly promoted the rapid development of the national economy.Because of the typical "three high-low" characteristics of coal seam gas in China,gas accidents are likely to occur in the gas control of working face.By means of data collection,theoretical analysis,software development,numerical simulation and industrial test,this paper has systematically analyzed the temporal and spatial evolution rules of mining fissure and the storage and transportation rules of pressure relief gas concentration area in gently inclined coal seams,which is of great value for the gas extraction of the low-permeability gently inclined coal seam.The main research contents are as follows:(1)The distribution characteristics of rock damage are acquired by analyzing the rock material composition,meso-structure and microstructure in the laboratory;with the adoption of uniaxial compressive,tensile and shear tests,the effects of loading time on rock strength are clarified by analyzing the failure characteristics of the initial damage;the coupling effect of the initial damage and loading rate on the rock damage is obtained by constructing the constitutive model;by employing the fracture toughness of rock fissure,the evolution mechanism of how the mining fissure open or close is revealed by analyzing the characteristics of fracture evolution under different loading modes.(2)Based on the technical conditions of the working face,the two-dimensional physical simulation test is carried out,and a reason,able image recognition method has been proposed to quantitatively analyze the evolution law of mining fissure.In the meantime,the effects of the mining speed and coal seam inclination on the distribution characteristics and evolution rules of open fissure and closed fissure are quantitatively analyzed in the numerical simulation.(3)The breaking mechanism of immediate roof and basic roof in inclined working face three areas is analyzed,the timing of the overburden breakage process of "O-X" in gently inclined coal seam is clarified,and the goaf filling characteristics of gently inclined coal seam are obtained.Morphological characteristics of the mining fissure in overlying strata of inclined working face are analyzed,and the effects of the key factors on the morphological characteristics are mainly analyzed by establishing the corresponding mathematical model.In the engineering practice,the temporal and spatial evolution law of mining fissure is analyzed by adopting the method of borehole television,microseismic monitoring and borehole concentration,constituting a "point+line+surface+body" integrated monitoring approach.(4)Based on the spatio-temporal evolution law of the mining fissure in gently inclined coal seam,this paper has analyzed the characteristics of the pressure relief gas source,and the migration characteristics of the pressure relief gas enrichment area during mining process are obtained;besides,the concept of advantageous channel of pressure relief gas is proposed,which provides a theoretical basis of pressure relief gas extraction in inclined coal face.(5)In view of the problems of high level borehole extracting pressure relief gas in advanced working face,how to achieve the balance between the stability of high level borehole and the efficiency of extracting pressure relief gas is mainly analyzed.Combined with the advantages of high level borehole and high drainage roadway,a reasonable extraction method for extracting pressure relief gas is proposed,which provides an effective method for pressure relief gas control.This study has analyzed the spatiotemporal evolution mechanism of the mining fissures in the gently inclined coal seam,established the mathematical model of elliptical banding,revealed the advantageous channel evolution mechanism of pressure relief gas storage,and further proposed a reasonable extraction method for extracting pressure relief gas.The above research results have been successfully applied in typical mines,which provides a theoretical basis for realizing coal and gas simultaneous extraction in the gently inclined coal seam.