| Based on systematic analysis of mine structure characteristics and its development laws, in this paper, structure of 3# Coal Seam has been identified using drilling logging curve with combination of regional structural features and its evolution. Also, the macroscopic and microscopic deformation characteristics of different types of tectonic coal in Xin Jing Coal Mine are discussed, together with their main geological factors in the development. Meanwhile, typical tectonic coal sample are selected to conduct the pressured-mercury testing, then gas characteristics and formation mechanism are analyzed. Finally, according to the mine gas content, structural curvature and tectonic coal distribution, impact of gas occurrence in Xin Jing Coal Mine has been discussed. Main findings are as follows:(1) After formation of coal bearing strata in Xin Jing Coal Mine, the area has mainly experienced three phases of tectonic stress including NS-trending in Indosinian epoch, EW-to-NWW-SEE trending in Yanshanian epoch, and NNE-SSW-trending in Himalayan epoch. Superposition and transformation of structural features during different periods form the dome, basin and saddle-shaped structures and so on.(2) Tectonic coal types in Xin Jing Coal Mine are more fully developed. Here, cataclastic, porphyroclastic, granulated, squamate, wrinkly and mylonitic coal can be seen. Different types of tectonic coal are formed under different stress-strain environment, and it is performed as special strain traces on macroscopic and microscopic deformation characteristics.Development of tectonic coal is affected mainly by small structure, therefore, its distribution continuity is poor. Additionally, cracks in tectonic origin, dirt band in coal seam and epigenetic erosion zone in coal seam also affects tectonic coal distribution.(3) With cluster analysis method, coal body structure of 3# Coal Seam has been divided into three categories, and characteristics of variation in each logging curve has been summarized, thus identifying 3# Coal Seam. Besides, destroy value of drilling coal body structure has been proposed and defined, also destroy value contour map of coal body structure in 3# Coal Seam has been performed.(4) It can be seen from the pressured-mercury testing that different types of tectonic coal are with different pore characteristics. From native structure coal to mylonitic coal, variation of total pore volume, porosity and median pore diameter displays a decreasing trend after the first increase, and pore specific surface area in the same type of tectonic coal sample shows stronger discrete characteristics, which results in an unstable overall trend. Native structure coal mainly contains and transition pores. With the degree of deformation increases, native pores have been destroyed, micropores have reduced, and macroscopic cracks and big holes have increased. Mercury curve in Xin Jing Coal Mine is divided into parallel type, sharp edge type, anti-S-type and double S-type, and the four types of pore structure represent four different types of pore morphology and connectivity, which leads to different degree of impact on gas migration and enrichment in coal seam.(5) Factors affecting gas occurrence of Xin Jing Coal Mine includes coal metamorphic grade, features of coal combination, coal seam buried depth, hydrogeological conditions, the role of coal in the epigenetic erosion, and heterogeneity distribution of coal structure under the control of coal mine construction has a significant effects on mine gas occurrence. |
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