ABSTRACT: The influence of reverse-dip displacement along low-dipping faults at the Underground Research Laboratory (URL) was assessed by constructing numerical models using both finite difference and distinct element methods. The URL was constructed by AECL Research to provide a realistic environment for in situ studies into aspects of the deep geological disposal of nuclear fuel waste. Fracture zones which intersect the URL shaft at depths of less than 300 m have a significant effect on the magnitudes of the measured horizontal in situ stresses. The numerical models discussed in this paper demonstrate that reverse-dip displacement along these near-surface faults is one factor leading to the observed near-surface reduction in stresses. The models also suggest that the horizontal stresses below the deepest fracture zone do not increase significantly with depth.

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