Radon emission evolution and rock failure

Previous experimental studies showed that the variation of Radon (Rn) emission is closely related to the development of rock deformation: Rn emission has a rapid increase with the growth of cracks and their surface areas (i.e. onset of fracture coalescence point), and reaches the maximum at rock failure. In this study, the stress level at the onset of fracture coalescence λ null null null null null null null null null null null null null null...