ABSTRACT
This work numerically analyses the rock pressures and deformations that develop in the medium to long term around tunnels for the storage of high-level radioactive waste in Switzerland, taking into account thermal and hydraulic effects. It is shown that the heat released as a result of radioactive decay has a significant effect; under the conditions of the planned deep Swiss waste repository, radioactive decay heat leads to twice as high lining loads and stresses, which calls into question the suitability of a conventional, practically rigid segmental lining. The main cause of the additional heat-related loading is the high excess pore pressure resulting from the combination of the high thermal expansion coefficient of the water with the extremely low permeability of Opalinus Clay. This effect is highly relevant also for a lining according to the yielding principle: the high excess pore pressure caused by the heat leads to lower effective stresses in the surrounding rock mass, lower resistance to rock shearing, greater irreversible deformations and greater tunnel convergences, which require a yielding support with a hardly feasible deformation capacity. In the present case, a high-deformability and high-strength segmental lining is necessary.
