The radon exhalation of rock samples under pressure

The behaviour of emanations of cylindric sandstone samples during the uniaxial load-test up to rupture was investigated. A temporary increase of the emanation rate up to 100% correlating with increased seismo-acoustic activity could be observed before the rupture. The emanation rate after the rupture changed by approximately 500% and the emanation coefficient by about 14%. The changes of the emanation rate before the rupture can be explained by a change of state of the sample, which cannot be sufficiently described by changes of pressure and length. A sudden change of the pressure and length of the sample should rather be considered as the initial moment of a slowly proceeding change of state only. However, it is impossible to give a definite answer to the question about the nature of these states. Obviously, the changes of the emanation coefficient after the rupture are due to an enlargement of the emanating surface. (author)