Computation of Strains and Pressures for Tunnels in Swelling Rocks

A three dimensional constitutive law for swelling rock is presented. It can be applied to the osmotic swelling of mudstone as well as to the swelling of rocks containing anhydrite. It describes the development of time-dependent strains and stresses due to swelling considering elastic and viscoplastic behaviour. Furthermore the anisotropic swelling behaviour is considered. This constitutive model was implemented within a numerical computation program according to the finite element method and calibrated with the aid of back-analyses of monitoring results in the exploration gallery of the Freudenstein tunnel which is completely located in the unleached Gypsum Keuper. A good agreement between numerical solutions and monitoring results could be achieved. Finally an outlook on a new design concept considering self-sealing effects around tunnels in anhydritic rocks is given