Rock characterisation facility (RCF) shaft sinking -: numerical computations using FLAC

Using FLAG and FLAC(3D), numerical computations were carried out to simulate a comprehensive pump test at Sellafield and to predict the hydro-mechanical consequences sinking of a shaft at that site might bring about. Transient discharge into the borehole could not be reproduced: however, the: reproduction of the post-transient flow was good. Shaft sinking was modelled with FLAC(3D). The mechanical as well as the hydrogeological effects of the planned shaft on its ruck surrounding, both near and far field. were typical and did not point to any difficulties that might be encountered had the shaft been constructed. By using new failure criterion, it was possible to capture the excavation damage zone by the simulations. It could not be captured by more established failure criteria such as Mohr-Coulomb or Hoek and Brown. Considering the assumptions made to set up the simulations. no coupling between the mechanical and the All Row computations was deemed necessary. (C) 2001 Elsevier Science Ltd. All rights reserved.