Radon Migration In Overlying Strata During Spontaneous Combustion Of Coal Underground And Its Application

Coal is an important basic energy and raw materials. More importantly, it is a non-renewable resource. The spontaneous combustion of coal, resulting in substantial waste of resources, threats to the safety of production. However, fire prevention has faced to great difficulties dut to the imperceptibility of fire and its hundred meters below under the ground. Therefore, it has been being a major worldwide problem to precisely detect the location of fire source. The measurement of radon isotope has been applied to many coal mines to detect fire source, but it is short of a complete theory. Therefore, radon migration law in overlying strata and its influencing factors are the keys to further enhance the precision of fire detection, showing the scientific significance and application value.The basic principle of radon migration was obtained on the basis of the analysis of the influcing factors on the radon migration. Using the largest self-developed spontaneous combustion of coal and radon laboratory bench, the migration mechanism of radon under overburden rock during the spontaneous combustion of coal underground, the characteristics of radon liberation at the different temperatures and in the different depth were systematically studied through experimental research, theoretical analysis and numerical simulation combined with on-site detection. The dangerous zone of the spontaneous combustion of coal in goaf was simulated. The abnormal regions of radon were analyzed according to detection on the ground.The main research contents and results are as follows:(1) The forming machnism of abnormal radon in overlying strata during the spontaneous combustion of coal. The forming machanism of abnormal radon was proposed on the basis of the combination of the effects of coal spontaneous combustion on radon in overlying strata and the "geogas" theory, according to the formation of radon, characteristics and sources.(2) The research and development of the spontaneous combustion of coal and radon bench. On the basis of the mechanism of radon migration, the spontaneous combustion of coal and radon bench was developed with the highest level of automation, which can be used to research the whole process of spontaneous combustion of coal with the different sizes and air leakage intensity, as well as radon libration laws in different media and under different construction conditions.(3) Research on the relationship between gases generated during the coal spontaneous combustion and the radon libration and the experiments on temperature field in the bench. The relationship between the index gases and the radon libration at the characteristic temperature was obtained. The relationship between the high temperature zones in different horizons and time and that between the high temperature zones in the centre measuring point and horizons, giving a guide for the arrangement of the radon measuring points during the coal spontaneous combustion.(4) Experiment of radon migration in overlying strata. The radon libration law in the different emanation media was studied during the spontaneous combustion of coal in the bench, giving out the effect of the porosity, temperature, position and depth on the radon libration.(5) On-site observation of the radon detection. The ground radon detection process, the data effective values and the analytical method were given. The relationship between the spontaneous combustion of coal underground and the abnormal radon amount on the ground through the on-site detection under four typical conditions, combined with the actual fire-fighting project results.(6) The numerical simulation of spontaneous combustion dangerous zone in goaf and the earth's surface radon libration law. Through long-term observation on gases in goaf on Wuda mining 1293 longwall working face, the danger zone was simulated with CFD, suggesting the consistency of spontaneous combustion dangerous zone with the on-site observation.