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.

gast project grimsel schematic drawing of experiment layout 02

Figure 1: Schematic drawing of experiment layout.

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

gast 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.

gast list of installed sensors

gast setup

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.

The GTS underground facilities are also available to interested 3rd parties for underground testing and research. The GTS offers cost-effective access to a fully developed, well characterised underground research facility with round the year logistical support - please contact Dr. Ingo Blechschmidt, Head of the Grimsel Test Site, for further details.