Stress pillar stability

Rinne M, Shen B, Lee H-S, 2003. Aspo pillar stability experiment. Part I Modelling of fracture stability by FRACOD. Part II Modelling Fracture Initiation and Acoustic Emission. Part III Reconstruction of Stress Field Using an Inverse Technique. International Progress Report, IPR-03-05. Swedish Nuclear Fuel and Waste Management Company, Stockholm, 2003. 

Rode mechanical stability. The main potential hazard to the integrity of an underground repository has its roots in rock mechanical failures. The stability of the repository depends on many factors, such as the volume of the rooms relative to the pillars. Convergence of rooms due to the plasticity of the salt and enhanced by the elevated temperature may cause stresses within the rock salt. It is therefore important that a repository at least for HLW should be built in a salt formation not mined before. Moreover, only the space required for a minimum number of years should be mined at the same time, and every room used up should be backfilled with crushed salt. On the other hand, convergence will help to eliminate open space in the rock salt quickly after rooms have been backfilled and will thereby be beneficial. 

As the stress increase, major fractures develop at the left side (unconfined), but the mid region of the pillar remains stable. The pattern of possible spalling from successive loading becomes more apparent though the pillar remains stable. In spite of the extensive fracturing at left side of the pillar, overall stability seems to be maintained after 120 days of heating. 

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