Study On Pore Gas Desorption Characteristics And Gas Occurrence Law Of 3# And 5# Coal Seam In Xiangshan Mine

Mine gas geological conditions in China is complicated,so different mining area of gas occurrence differ in thousands ways,mining for coal and gas accident in northern shaanxi Seoul highlight areas,especially in the area of the soft layer of coal seam gas enrichment are prone to accidents,and mine south xiangshan mine coal and gas outburst accident did not,but its production suffered serious constraints of mine gas.Accurately mastering the desorption characteristics and occurrence law of gas in Xiangshan mine is an important guide for targeted gas control and a key problem for ensuring mine safety and efficient production.In this thesis,the soft and hard stratified coal samples of 3^#and 5^#coal seams in Xiangshan mine were collected,and the pore structure characteristics and gas desorption characteristics of 4 groups of coal samples were tested through laboratory experiments,and the internal relationship between them was studied.Through data collection,field measurement and theoretical analysis,the influential factors of gas occurrence in Xiangshan Mine were studied with Spss software,and the gas content and distribution in the south No.1 and South No.2 mining areas were predicted.The main conclusions were as follows:(1)The ash content and porosity of soft stratified coal samples in 3^#and 5^#coal seams are higher than that of hard stratified coal samples.Thefvalue of soft stratified coal samples in 3^#and 5^#coal seams is lower than that of hard stratified coal samples and less than 0.5,and the value of?p is higher than that of hard stratified coal samples and greater than 10mm Hg.Compared with hard stratified coal samples,soft stratified coal samples of 3^#and 5^#coal seams have more coal and gas outburst risk.(2)The curves and data of mercury injection method and nitrogen adsorption method show that there are a large number of closed and semi-closed pores in the soft and hard stratified coal samples of 3^#and 5^#coal seams,and the pore connectivity is poor.The pore volume and specific surface area of soft stratified coal samples are more developed than that of hard stratified coal samples.In terms of pore volume distribution,3^#and 5^#coal seams soft and hard stratified coal samples have the most developed large pore volume,small pore and micro pore volume are more developed,while the middle pore volume is not.The total pore volume proportion of 3^#and 5^#coal seams soft stratified coal samples in small and micro pores is 10.22%and 5.07%higher than that in hard stratified coal samples.The damage of geological structure makes the pores and micropores of soft stratified coal samples develop further,and the pore volume of soft stratified coal samples is more developed.In terms of specific surface area distribution,the micropore specific surface area of soft stratification of coal seam 3^#and 5^#is more developed.The fractal dimension D₁indicates that the surface of soft stratified coal sample is coarser,while the fractal dimension D₂differs little from that of hard stratified coal sample,indicating that the internal pore structure of soft and hard stratified coal sample is more complex.(3)The desorption capacity and desorption velocity of soft stratified coal samples in 3^#and 5^#coal seams are greater than that of hard stratified coal samples at different equilibrium pressures and different desorption stages,and the gas desorption capacity of soft stratified coal samples is stronger than that of hard stratified coal samples.The increasing gas equilibrium pressure has a significant influence on the desorption capacity of soft and hard stratified coal samples at the initial stage of gas desorption.There is a close positive correlation between coal gas desorption capacity and pore volume and specific surface area.The coal with more uneven pore surface,coarser pore structure and simpler pore structure has stronger initial gas desorption capacity.(4)The difference of tectonic environment between north and south of Hancheng mining area has certain control effect on gas migration and enrichment in 3^#and 5^#coal seams.Geological structure and burial depth are the main controlling factors of gas occurrence in coal seam 3^#and 5^#of Xiangshan Mine.The burial depth has a significant positive influence on the gas content of 3^#coal seam in Xiangshan Mine,but has little influence on 5^#coal seam.The sandstone thickness within 10m of the roof has a significant negative influence on the gas content of 3^#and 5^#coal seam,and has little influence.The thickness of coal seam has a significant positive influence on the gas content of 5^#coal seam,but has little influence on the gas content of 3^#coal seam.It is predicted that the gas content is high in the northwest and southwest of the first and second mining areas of Xiangshan 3^#coal seam,and the highest predicted gas content is7.21m³/t.The gas content is high in the southwest of the second mining area of Xiangshan 5^#coal seam,and the highest predicted gas content is 10.41m³/t.There are 39 figures,20 tables and 75 references in this thesis.