The On-Going Pillar Stability Experiment at the Äspö Hard Rock Laboratory, Sweden

Abstract A Pillar Stability Experiment, is currently planned for SKB's Aspo Hard Rock Laboratory. The objectives of this experiment are: demonstrate the capability to predict brittle failure (spalling) in a fractured rock mass, demonstrate the effect of backfill (confining pressure) on the brittle failure response, and compare 2D and 3D mechanical and thermal numerical predicting capabilities. The 1 m thick pillar will be located between two large vertical boreholes. Preliminary modelling of the experiment has been carried out with Examine3D, FLAC3D, FRACOD and JobFem. The 2D and 3D numerical results are similar and indicate that a temperature increase of approximately 40–50 degrees C is sufficient to initiate spalling. The field part of the experiment is scheduled for completion by May 2004.