Experimental Study On Coal And Gas Outburst In Strong Outburst Coal Seam With Different Moisture Content

Coal and gas outburst is an extremely serious dynamic phenomenon under the comprehensive action of many factors.According to relevant data and literature at home and abroad,water content has a significant impact on coal and gas outburst.Therefore,on the basis of studying the gas occurrence law and outburst disaster characteristic analysis of the Luling 8 coal seam,this paper selects the coal sample of the Luling 8 coal seam,firstly carries out the influence test on the physical parameters of coal body under different water content conditions,researches and analyzes the influence law of gas desorption law and outburst prediction multiple indexes under different water content conditions,and provides the theoretical basis for studying the simulation experiment of coal and gas outburst.Then,coal and gas outburst tests under different water content conditions are carried out to simulate the outburst process and analyze the outburst test results.Finally,the outburst energy calculation and prevention countermeasures are carried out for the outburst test of the No.8 coal seam in the Luling coal mine.The main conclusions obtained in this paper are as follows:1)There were 26 coal and gas outbursts in the Luling Coal Mine,and even the accident of throwing tens of thousands of tons of coal and rock and millions of m3 of gas occurred.The outburst disaster accident mainly occurred in the geological structural zone,which was mainly composed of inclined cut-off layers.A total of 58large and medium-sized faults with a drop of more than 20m were found,and a large number of small faults were also found.The thickness of coal seams varied greatly,and folds or faults often existed near the outburst point.Due to the huge destructive effect of geological structural movement on coal mass,most of the coal mass in the outburst area was almost broken or even in a powder state,so geological structure was probably the main factor causing coal and gas outburst in the mine.With the deepening of mining depth,various conditions of coal seam make gas sealed and well preserved,resulting in high gas content and high gas pressure in coal seam.The occurrence of medium-sized and large-sized coal and gas outbursts in depth,which are dominated by geological structure and gas pressure,leads to the increase of the frequency and shortening of the period of coal and gas outbursts,and the rapid increase of the outburst intensity.Therefore,coal seam gas is also one of the main factors causing coal and gas outbursts.2)The experimental results of different water content on coal gas desorption show that water content and equilibrium pressure have significant influence on coal sample gas adsorption and desorption.When the adsorption equilibrium pressure is4MPa at the maximum and the water content of coal sample is 1.68%at the minimum,the cumulative desorption amount is 4.3186m³/t at the maximum.With the increase of water content of coal sample and the decrease of equilibrium pressure,the cumulative desorption amount has an obvious decreasing trend.When the water content of coal sample increases to 6.83%and the gas pressure drops to 0.74MPa,the desorption amount is 0.7669m³/t at the minimum,indicating that water has a significant inhibitory effect on gas desorption.When the equilibrium pressure is the maximum and the coal moisture content is the lowest,the average desorption rate of coal sample in the first 1min is the maximum of 0.6339 m³/?t·min?.At this time,the desorption amount of gas per unit time of coal is the largest.With the increase of moisture content and the decrease of gas pressure,the initial desorption rate obviously decreases,and with the progress of coal gas desorption process,the desorption rate of coal sample slows down from fast to slow,and the desorption amount per unit time changes less.3)The results of coal and gas outburst tests with different water content show that water content and gas pressure have different effects on the migration of outburst coal,outburst strength and characteristics of outburst holes.After the outburst occurred,the shape of the thrown coal body on the ground showed shuttle type distribution,of which the coal quantity near the outburst mouth was very small,the middle area was slightly blank,and the vast majority of coal powder was distributed in the far area,indicating that the regularity of coal and gas outburst was very obvious.In the three groups of tests where outburst has occurred,when the water content is the lowest1.47%and the gas pressure is the highest 0.45MPa,the outburst phenomenon is the strongest,and the outburst intensity is the highest 26.47%,which shows that the coal outburst amount is the highest 5.714kg,the outburst distance,the outburst width,the outburst hole and the outburst model are the largest,and the coal body around the hole is damaged to a high degree and the damage area is large.As the water content increases to 5%,the outburst intensity decreases.When the water content of coal body continues to increase to 10%,the outburst does not occur,which indicates that the water content has a significant impact on the occurrence of outburst,the outburst intensity and the characteristics of outburst holes.When the moisture content of the test coal mass is 1.47%,the outburst process with low gas pressure of 0.25MPa does not occur,and when the gas pressure is increased to 0.35MPa,the outburst process occurs,which indicates that there is a critical gas pressure value for coal and gas outburst,and with the gas pressure increasing to 0.45MPa,the outburst intensity increases,the degree of damage to the coal mass becomes higher,and the outburst holes and models become larger.4)The outburst energy is defined as the mass of outburst coal at different distances multiplied by its throwing distance,of which the outburst intensity of coal and gas in test 3 is the largest,so the total outburst energy is calculated to be the largest,with a value of 62.123Kg·m.Through the impact test of coal outburst prediction index under different water content conditions carried out in the laboratory,the data fitting analysis is carried out on the firmness coefficient,the initial speed of gas diffusion and the impact curve of drill cuttings gas index?h₂,and then the critical value of outburst prediction index is compared to determine that the water content interval of coal with hydraulic outburst prevention measures is greater than 5%.There are 40 pictures,16 tables and 65 references in this paper.