Study On Evolution Law Of Temperature And Impact Force Of Coal And Gas Outburst In Deep Coal Mines

With the depletion of shallow resources in China,it has gradually entered deep mining.The occurrence mechanism of deep coal and gas outburst is bound to be significantly different from that part.Deep outburst characteristics cannot be accurately analyzed by shallow outburst.The accuracy of outstanding early warning is restricted by its unclear occurrence mechanism.Therefore,this paper took the similar simulation test of deep coal and gas outburst as the main research line.The scientific problems were unclear change rule of deep outburst monitoring means and imperfect prediction indexes.The outburst coal seam of Pingdingshan No.11 Coal Mine and Sunjiawan high gas coal seam of Hengda Coal Mine were taken as the research objects.The buried depths of 600 m,800m,1000 m,1200m,1400 m and 1600 m were considered.Temperature monitoring,impact monitoring and acoustic emission signal monitoring were used.Firstly,the deep outburst phenomenon,the comparison of outburst parameters between briquette and raw coal,the change law of temperature,the change law of impact force,and the change law of acoustic emission signal were studied.Secondly,the correlation between outburst parameters such as critical gas pressure and test effective stress and temperature and impact force were analyzed.Finally,according to the characteristics of acoustic emission signal in four periods and the relationship between acoustic emission signal and temperature variation,the risk index of coal and gas outburst was established,and the relationship between acoustic emission signal and impact force was discussed.The research results can be used as reference for mechanism and risk prediction of deep coal and gas outburst.The results showed that:(1)When the ratios of different briquettes in coal mines were the same,the relative outburst strength changed at the same numerical level,and it was found through the comparative analysis of three coal samples.The same selection of raw coal and briquette specimens in coal mines had a significant impact on the relative outburst strength,but the overall trend was the same.The critical depth of Sunjiawan coal seam in Pingdingshan No.11 Coal Mine and Hengda Coal Mine is determined to be 1000 m.Raw coal outburst more intense,more dangerous.(2)In the whole process of outburst inoculation,the largest decrease of temperature variation was the first section near the outburst outlet.The falling time was earlier than the falling time of gas pressure.The decrease of temperature variation occurs when outburst holes or outburst weak surfaces were formed,indicating that the use of temperature can predict the occurrence of coal and gas outburst earlier.Considering different buried depths,it was found that the peak temperature variation decreased with the increase of buried depth.It showed that under the action of high ground stress,the outburst gestation time of deep coal body was shorter,and it was more prone to failure than shallow.(3)In the evolution process of coal and gas outburst,the stress and damage degree of coal body in the inoculation stage affected the propagation characteristics of impact force in roadway after outburst.The impact force experienced the evolution process of ’ rising-peak-stable fluctuation-decreasing-rising ’.It had obvious pulse phenomenon.The impact force increased with the pulse phenomenon.There was a corresponding transformation relationship between the peak impact force and the gas pressure,which decreased with the increase of the effective stress of the test and increased with the increase of the critical gas pressure.It showed that the energy of impact force was mainly derived from gas internal energy.At the same time,the pulse phenomenon was occurred when the ringing count of acoustic emission increased sharply.But the pulse phenomenon did not necessarily appear the sharp increase of acoustic emission ringing count.It showed that there was a corresponding relationship between impact force and acoustic emission signal.Acoustic emission signal reflected the rupture of coal body in outburst inoculation.Impact force reflected the coal fragmentation and risk intensity after outburst.Both of them can monitor the outburst synchronously.(4)Based on the analysis of the relationship between acoustic emission signal characteristics and temperature variation,the cumulative acoustic emission ringing count P,average acoustic emission ringing count N,and the difference between acoustic emission ringing count and temperature variation decline time point S were established.The paper has 54 figures,9 tables,and 119 references.