Study Of Tectonized Coal Texture And Its Controlling Mechanism Upon Gas Properties

Tectonized coals with various deformation types and extents were collected mostly in Huaibei area, which is the main study area. On the basis of overall characterization of coal samples on macro- and microscopic scales and vitrinite reflectance measurements, in combination with geological analyzes of study region, mining area and coal mines where the samples were collected and present achievements on classification of tectonized coals, the tectonized coal types of each collected samples were determined properly, and 23 tectonized coal samples with low, middle and high coal rank and various deformation types and extents were selected for experimental and theoretical study, the texture of tectonized coal and its controlling mechanism upon gas properties were intensively discussed, which provides important theoretical supports for forcasting the law of gas occurrence and gas outburst in coal mines.Textural analysis methods, such as scanning electron microscope (SEM), X-ray diffraction (XRD), electronic paramagnet resonance (EPR), nuclear magnetic resonance (NMR) and fourier transform infrared ray (FT-IR), experimental measurement techniques for gas properties, such as mercury intrusion porosimetry (MIP), liquid nitrogen adsorption, carbon dioxide adsorption and isothermal adsorption and desorption, were applied to selected coal samples for determining the evolutional characteristics of ultramicro and molecular texture and gas properties of tectonized coals with different coal ranks and deformation types and extents, the evolutional mechanisms of tectonized coal texture at different coal ranks and their controlling mechanism on gas properties of tectonized coal, such as pore structure, adsorption and desorption properties, and gas occurrence and outburst were intensively studied. Associated elements analysis of coal and a method to determine the pore compressibility were introduced to tectonized coal study, the effect of tectonic dynamics upon elemental occurrence and the pore compressibility of tectonized coal and its control on gas extraction were systematically discussed.Results show that, the textural evolution mechanisms of tectonized coal of different coal ranks and deformation types are significantly different, deformation make the macromolecular aliphatic chain break and the functional groups fall in coals with low and middle coal ranks, strong ductile and shear deformation cause unpaired electrons bond, which is useful for aromatic ring development of coal with low and middle coal ranks, as for coals with high coal rank, the effect of deformation of all of types is to break the integrity of aromatic nucleus vertically and horizontally in different extents. Some associated elements and their combination might be used as indicator of stress-strain environment, used for determining the type of stress-strain environment where the tectonized coal is formed and deformation extent depending upon their concentration in tectonized coal. Textural evolution of tectonized coals of various deformation types and coal ranks show different controlling mechanism upon pore volume and specific surface of pores with different pore diameters, deformation control the amount of pore volume and specific surface of macropores and meso-, micropores by affecting the development of cleats and ordered extent of molecular structure in coals, respectively. The shape of macropore varies as the deformation type and extent change, weak brittle cataclasm deformation leads to sparsely-developed cleats, medium brittle cataclasm and shear deformation and weak ductile deformation are helpful for significant increase of open pores, strong brittle cataclasm and ductile deformation will break the pore system and connectivity, and cause flask pore develop. The difference of adsorption properties of tectonized coals with various deformation types depends upon the amount of pores in certain range of pore diameter. The effect of tectonized coal type upon gas occurrence and outburst is quite different, selected tectonized coals were classified as no outburst, weak outburst, outburst and strong outburst tectonized coal, according to their gas properties, corresponding to probability of coal and gas outburst from weak to strong.