(GRS-745) Sandwich-HP - Vertical Hydraulic Sandwich Sealing System

K. Wieczorek (GRS), K. Emmerich (KIT-CMM), T. Nagel (TUBAF), E. Bakker (KIT-CMM), R. Diedel (SSKG), M. Furche (BGR), J. L. García-Siñeriz (Amberg), U. Glaubach (IBeWa), J. Hesser (BGR), M. Hinze (GRS), M. Hofmann (TUBAF), D. Jaeggi (swisstopo), F. Königer (ISU), J. C. Mayor Zurdo (Enresa), L. Räbiger (IBeWa), M. Rey Mazón (Amberg), C. Rölke (IfG), P. Schädle (ENSI), R. Schuhmann (ISU), H. Shao (BGR), S. Tuñón (Amberg), M. V. Villar Galicia (Ciemat), T. Wilsnack (IBeWa), R. Yeatman (BDS)

Förderkennzeichen 02E11799A, 02E11799B und 02E11799C

An important component for the closure of deep geological repositories (being accessed by a shaft) is a shaft sealing system which limits the fluid inflow from the adjacent rock to the repository in the early post-closure phase and delays the release of possibly contaminated fluids from the repository at a later stage. The KIT-developed Sandwich sealing system is a multi-component barrier which can contribute to this sealing function and is considered as part of the shaft sealing concepts for a final repository of radioactive waste in Germany.

The Sandwich sealing system consists of alternating sealing segments of bentonite and equipotential segments that are characterized by a high hydraulic conductivity. Within the equipotential segments fluid is evenly distributed over the cross section of the seal. Water bypassing the seal via the excavation damaged zone, or penetrating the seal inhomogeneously, is contained and a more homogeneous hydration and swelling of the sealing segment is obtained.

The functionality of the system has already been proven in semi-technical scale experiments. It was the aim of this project to install a large-scale in-situ experiment that addresses the interaction between the sealing system and the host rock. The experiment at the Mont Terri rock laboratory consists of two experimental shafts in which Sandwich sealing systems have been installed. The sealing systems can be saturated from pressure chambers located at the shaft bottoms via inclined lateral feeding boreholes. The seals and the surrounding rock will be intensely monitored.

The experiment objectives were to demonstrate the feasibility of installation, to investigate the saturation process, to qualify measurement and monitoring techniques, and to assess the sealing effectiveness. Particularly, the investigation of the long-lasting saturation process and the latter two objectives will be pursued in follow-up projects. The insitu work was complemented by a laboratory testing campaign for material characterization, by further semi-technical scale experiments and model simulation.