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Title An Innovative 3-D Numerical Modelling Procedure for Simulating Repository-Scale Excavations in Rock ? SAFETI

Authors R. P. Young, D. Collins, J. Hazzard, A. Heath -University of Liverpool, Department of Earth Sciences, UK. W. Pettitt, C. Baker - Applied Seismology Consultants Ltd., UK. D. Billaux, P. Cundall, D. Potyondy, F. Dedecker - Itasca Consultants S.A., France. C. Svemar - SKB, Sweden. P. Lebon ANDRA, France.

Publication Reference SAFETI, Seismic Validation of 3-D Thermo-Mechanical Models for the Prediction of the Rock Damage Around Radioactive Spent Fuel Waste. 2003, Midterm Progress Report to EU.

Abstract The combination of numerical modelling and observational validation has led to significant recent advances in our understanding of the evolution of the Excavation Disturbed Zone. However, most applications of numerical modelling to repository excavation problems are restricted in that they either (i) involve rather simplistic models that do not account for the detailed response of the rock with time or (ii) consider more complex models but are restricted to small scales and/or 2-D cases. The SAFETI project (currently being undertaken within the Euratom scheme) is developing a highly innovative code that will allow a more ?realistic? simulation of repository excavations in 3-D to be carried out.

The project has resulted in a new modelling code, termed AC/DC (Adaptive Continuum/ DisContinuum). The discrete element (discontinuum) portion of the code is based on the PFC3D code developed by the Itasca Consulting Group. The code works by initially considering the rock mass as a continuum. As ‘elements’ of the rock- mass respond to stress from excavation disturbance (or other influences) these convert to a discontinuum response in order to track the development of cracking as it occurs. The code has been developed to run on the multiple-node parallel super-computing facility (NESSC) at Liverpool University. This allows significantly larger-scale simulations to be run than have been possible to date.

The AC/DC codes are undergoing calibration and validation as part of the SAFETI project. This has involved a comprehensive set of laboratory tests where mechanical, velocity and acoustic emission (AE) data have been collected and simulated. The next phase of the project will compare numerical simulations and actual in-situ velocity and AE data from a field-scale experiment. It is expected that the AC/DC method will become a powerful tool for the predictive and diagnostic modelling of rock-mass response for use in future repository design and operation.

Key Figure Key Figure
Figure 2: A screen capture of the software ACDCvis, showing a cutting plane through a 4200 ball model of granite at a time step in an axial compression test. The tensile and shear cracks and model balls are displayed. The various user-controlled analysis options are accessable in the menu on the right.

Link ./files/publications/safeti_lux_2003.pdf



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