Research On Radon Emanation During Deformation And Failure Of Loaded Coal And Rock

With the increasing of mining scale and depth, the coal dynamic disaster such as coal and gas outburst in deep mining became more and more serious. According to related studies, coal and rock failure often was accompanied by energy dissipation as well as emission of radionuclide. Therefore, the changes of radon concentration could provide a prospective method to predict coal and rock dynamic disasters. In this paper, we measured the content of nature radionuclide in coal and rock, analyzed the influence factors of radionuclide occurrence, introduced the level of radon distribution in coal mine, and studied the effect of mining face to radon emanation. In addition, this paper displayed an experiment system of radon measurement in failure process of coal and rock, through which we studied the stage characteristics of radon emanation during the fracture of coal and rock in uniaxial compression. The main conclusions are as follows:(1) This paper displayed an experiment system of radon measurement in failure process of coal and rock which could measure the change of radon emanation due to coal and rock failure, including triaxial compression system, acoustic emission experiment system as well as radon concentration determination system. Based on this system, we studied radon exhalation during deformation and fracture of coal rock under compression through changing axial stress, collecting stress-strain and acoustic emission, and measuring radon concentration under different stress conditions. The research results indicate that: the self-developed system had some advantages such as high sensitivity, quick measurement, diversiform monitoring means, and simple operation, and the experimental measurement results were reliable.(2) The radon emanation occurred clear phase variation during the deformation and fracture of coal and rock in uniaxial compression: ① Radon emanation had a big increase with the original state due to large quantity of micro fissure close at the beginning of loading. ② When deformation was elastic, radon emanation decrease with the primary period of loading, however, most experimental specimen had a slightly increase with the original state. ③ With the axial stress increased further, coal and rock samples appeared plastic deformation, in which radon emanation rise greatly. ④ It was also found that the radon emanation increase was even more obvious after samples failure.(3) In order to analyze the relationship between radioactivity and metamorphic grade of coal and rock, we measured the radioactivity of coal and rock and studied the coal proximate(moisture, ash, volatile) influence on radioactivity. The measurement results showed that not only the degree of coal and rock metamorphism, but also the content of coal and rock ash related to radioactivity of coal and rock.(4) In this paper, we studied radon emanation in producing mines, and analyzed the sources and statistic distribution of radon underground coal mine. In order to explore the sources and statistic distribution of radon in Ju Lishan coal mine, We mainly studied the change of radon emanation due to mining influence, which supply the feasible basis for radon monitoring about coal and gas outburst and other dynamic disaster.The research results indicated that there was a clear phase variation in radon emission during uniaxial compression, and the radon could be treated as the precursory characteristics of coal and rock failure. The research results also provided an effective means-testing and theoretical support for predicting and forecasting coal and gas outburst and other dynamic disaster.