Under German law, the crack damage stress must not be reached at any time during the operation or post-closure phase of a nuclear waste repository. This legal requirement can only be fulfilled if the parameter can be measured precisely. We have thus developed a new measurement technique, which overcomes the limitations of the conventional method. In combination, old and new method offer an easy procedure to detect the crack damage stress in fully saturated rocks in a fast and robust manner.

Computer simulations are used to understand processes in nuclear waste disposal. The results are used to judge the safety of waste repository. Not all the information needed for such analyses, e.g. rock properties, is precisely known, contributing to uncertainty in the analysis results. We are interested in understanding the effect of the uncertainty of input quantities and of certain simplifications made during model creation on the outcome of computer simulations.

The current site selection process foresees 11 months for the laboratory analysis of geomechanical rock properties. Given the low permeability of claystones, paying heed to the hydromechanical coupling which governs all geomechanical processes slows down the lab experiments on claystones considerably, compared to other rock types. We show how to carefully plan the experiments and how to identify synergies in order to stay within the time frame of the site selection process.

The SW-A experiment is a large-scale in situ test at the Mont Terri rock laboratory that implements a vertical hydraulic shaft-sealing system in argillaceous host rock. The response of the system and the surrounding rock to hydration is examined. The experiment objectives are to demonstrate the feasibility of installation, to investigate the saturation process, to qualify measurement and monitoring techniques, and to assess the sealing effectiveness. Recent data and experience are presented.

A Sandwich shaft sealing system consists of alternating sealing segments (DS) of bentonite and equipotential segments (ES) with a high hydraulic conductivity. Water accessing the system results in swelling of the DS. Within the ES the water is evenly distributed over the cross section of the seal. Thus, swelling is more homogeneous and seal bypass is reduced. At the Mont Terri rock laboratory, this sealing system is tested in connection with the host rock in a large-scale in-situ experiment.