The full-scale low-pH shotcrete plug was constructed in 2007 in the context of ESDRED and the TEM project has been part of the experiment set-up right from the start. While the overall goals are to demonstrate the construction feasibility and to test the support capacity of the plug, the particular objectives of the TEM project have been:
- To investigate the efficiency of an existing wireless magneto-inductive (MI) transmission technique and
- To evaluate seismic tomography as a non-intrusive monitoring technique.
In addition, the TEM instrumentation provides supplementary data for the hydration process in the bentonite buffer.
Since 2009 these objectives continue to be pursued in association with MoDeRn.
In the current experiment set-up the monitoring concept encompasses three completely separate systems to measure and compile data concerning total pressure, pore pressure and water content in and around the plug and bentonite section:
- A conventional system with sensors being connected to the data acquisition unit via cables
- A wireless system which uses a magneto-inductive technique to transmit data from a data logger “in” the core of the experimental set-up to a data acquisition system in its vicinity
- Non-intrusive seismic tomography which employs 6 boreholes positioned at a certain distance around the low-pH shotcrete plug.
Perspective view of the experimental layout and monitoring installations
Test and Evaluation of Monitoring Systems (ESDRED / TEM)