Radon Release from Underground Strata to the Surface and Uniaxial Compressive Test of Rock Samples

The mechanism and critical conditions of rock failure in underground coal mining processes have attracted great attention. Based on the origin and properties of radon gas, we propose that radon release from underground strata to the surface occurs in two stages, i.e., the formation of free radon and the migration of radon gas. Due to its optimal combination of efficiency and low background measurements, the α-ray measurement was employed to measure radon gas from rock fracturing. The uniaxial compression of rock samples and the concentrations of radon emanating from the loaded samples were experimentally investigated. The results revealed that radon concentrations are negatively related to uniaxial loads and elastic deformations, provided compressive failures are not observed. As the loads increase, the stabilization duration and internal porosity of rock samples get decrease, which result in reduced radon emanation. When the load gets more than the limit strength of rock samples, the radon concentrations increase significantly and eventually reach the maximum value, and then slightly decrease and approximately tend to be stable. Finally, a preliminary correlation between the complete stressstrain process of uniaxial loaded rock samples and the concentration of radon emanated was presented, which needs further experimental validations. Even so, we believe that the failure mechanisms of mining-induced overburdens could be investigated based on radon gas concentrations. ARTICLE INFO