Disturbed and damaged zones around underground openings - effects induced by construction and thermal loading

The excavation of underground openings will induce rock failure in their vicinity. The size of such an excavation disturbed or damaged zone and the impact on hydraulic properties is controlled by the local (secondary) stress state, the pore pressure development and the physical properties of the host rock. Besides the geometry of the opening itself and the excavation/support techniques used, a significant impact on the geometry and characteristics of the EDZ is caused by the heterogeneity and the potential anisotropy of the host rock. Laboratory testing and large-scale in-situ mine-by experiments provide an understanding of the time-dependent development and potential self-sealing processes of the EDZ for different host rocks. Numerical blind predictions and back-calculations (e.g. within the EC projects Modex-Rep, CLIPEX and NF-PRO) have increased the confidence in the understanding of the underlying processes. After emplacement of waste in a repository, the rock experiences thermal loading. Stress and pore pressure will change and may alter the EDZ. New EC projects (TIMODAZ, THERESA) have been initiated to extend the geoscientific data bases for an in-depth understanding of THM coupled processes and to provide advanced modelling capabilities for assessing the evolution of the EDZ before and after closure of the repository structures.