Study On The Acoustic-electric Effect Of The Coal In Heating Injury Process

Mine fire is very serious, threatening the lives and safety of the general miners, wasting alot of coal resources. Therefore，it is very important to monitor and Prevent the mine fire.Currently Acoustic emission has been widely used in forecasting the deformation and fractureof coal and rock, and the studies of coal and rock potential monitoring also have beendeveloped. Acoustic emission and potential signals will be produced in heating process, so it isvery meaningful to study the Acoustic emission and potential signals variation of coal androck in heating process.In this paper, the researcher has used warm deformation damage electrical effectsexperiment system, testing AE and potential signals of small size coal samples, studying AEand potential characteristics of small size coal samples during heating, analyzing the influencebetween volatile and AE and potential signals; The researcher has also establishing warmdeformation damage electrical effects experiment system of coal heap, testing the surfacetemperature of the coal heap, studying the AE and potential signals of measuring points andthe impaction on the distance to the heat source. Then combining with the thermal crackingcharacteristics of coal, the AE and potential mechanism are analyzed in the injury heatingprocess. The main results of this paper are:(1)Throughout the hole heating process, the AE signals of small size coal samples areincreased at first and then slowed down, at last kept stable, potential signal showing theweak-gradual increase characteristic; Compared with the little volatile coal, the potentialsignals of large volatile content coal have greater change at the beginning of the heatingprocess, the rising trend of AE signal is more obvious, and during the experiment AE andpotential signal have larger magnitude change.(2)At the beginning of the heating process, the surface temperature of coal heap isconsistent, then followed by scattered high-temperature region, along with the heating, hightemperature region are gradually concentrated in the center of coal heap(3)Coal heap sample can generate AE and potential signals during heating. There is agood correspondence between AE and potential signals of each measuring point. When thesurface temperature of coal heap is below80degrees, the AE and potential signals are veryrare; when the surface temperature of coal heap is80~120degrees, the AE and potentialsignals become active. When the temperature is greater than120degrees, the AE and potential signals keep growing until reaching the maximum value of AE and potential signals.(4)The AE and potential signals change trend of measuring point which have the samedistance to the heat are roughly the same. Compared with the short distance measuring points,the long distance measuring points have large temperature, during the experiment AE andpotential signal have larger magnitude change. There is a good agreement between AE andpotential signal for each measurement point and as long with the increase of AE signal, thepotential signals also increase.(5)Thermal stress forces internal fracture of coal or rock and makes it friction anddislocation between particles, resulting the AE and potential signals； Furthermore, theelectron kinetic energy overcomes the escape function, a large number of electron escapesfrom coal which also has a role to the potential signal.