The Study On Pore Characteristics And Adsorption Desorption Performance In Fault Structure Area Of Qingdong Coal Mine

With the continuous mining of coal mines in China,the mining depth gradually transits from shallow to deep,the geological structure of deep strata is more complex,the coal seam thickness changes unevenly,and the index parameters of coal seam gas outburst are higher and higher,which makes the possibility of coal and gas outburst greater and greater.The statistical results of a large number of accident cases show that the vast majority of coal and gas outbursts occur in structural coal seams.Tectonic coal is under the action of geological structure,the coal body is broken and crumpled under the action of tectonic stress,and the pore structure is transformed,so that its adsorption and desorption performance is changed.Tectonic coal is an important factor of outburst.In order to further explore the relationship between tectonic action and outburst,this paper selects two groups of coal samples in different complex structural zones,systematically compares pore structure and gas adsorption desorption performance,and makes a connection between drilling cuttings gas desorption indexes K₁ and?h₂.The main conclusions are as follows:(1)Characteristics of Pore structure,four groups of coal samples are ink bottle pore or sealed at one end of the main air-tight pores.The pore size distribution of four groups of coal samples are all inclined to Micropore,the order of Micropore size is much larger than other pore size,the development degree of Middle Pore and macropore is lower,the pore volume and specific surface area of QZ coal sample are larger than YS coal sample.The fractal Dimension D₁?D₃and D₄ of QZ coal are bigger than that of YS coal,which indicates that the surface roughness and pore structure of Qz coal are higher.It can be seen that Qz coal sample is more complicated under the influence of strong tectonic action,and its micropore and macropore are more developed than YS coal sample.(2)In terms of adsorption and desorption characteristics,under the same pressure,the limit adsorption capacity and adsorption constant a of QZ coal sample are higher than YS coal sample,the initial desorption capacity and 120min accumulative desorption capacity are also higher than YS coal sample,the effective diffusion coefficient is 2.9?7.9 times of YS coal sample.It shows that the adsorption and desorption ability of QZ coal sample is further enhanced under the action of complex structure.Based on the study of the relationship between Pore structure and adsorption-desorption characteristics,it is further verified that the micro-pore structure is the main factor affecting the adsorption performance,while the large pore structure plays a major role in the gas desorption ability.(3)The drilling cuttings desorption index aspect,The desorption parameters K₁?(?)h₂were positively correlated with the adsorption constant a,and positively correlated with the adsorption constant b,but gradually became stable with the increase of b.The desorption indexes K₁ and(?)h₂of QZ coal are higher than that of YS coal,and the reliability of(?)h₂ is better than that of K₁.Under the action of strong tectonic stress,the pore structure of QZ coal sample is more developed and its initial gas desorption ability is stronger,which leads to the increase of error in the experiment and the lower reliability of K₁.The dissertation has 62 figures,24 tables and 121 references.