Gas-Permeable Seal Test - Setup and design
The experiment design was finalized after numerous material evaluations had been done in the first phase of the project.
The gas-permeable seal itself consists of 23 horizontal layers (10 cm in height) of compacted sand/bentonite (S/B ratio 80/20) with a length of 8.0 m and a diameter of 2.3 m. Vertical sand filters on either end serve for initial water and later gas injections. The S/B is surrounded by granular bentonite material (GBM) to avoid water or gas bypass. On the back end the setup is closed off against the tunnel face by a concrete element. Towards the open tunnel there is a pressure containing concrete plug.
Bulk material parameters
The setup facilitates 17 instrumentation sections with sensors to monitor the sealing behaviour during saturation and the gas transport capacity in the later gas invasion phase as well as the effects on the host rock (hydraulic) and the curing and movements of the concrete plug.
List of installed sensors.
a) Instrumentation tree and compaction of a lower layer of sand/bentonite. b) Cross-section through 3D CAD model showing surfaces of selected S/B layers and sensor positions c) Experiment layout with instrumentation sections indicated in red.