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Please use this identifier to cite or link to this item: http://hdl.handle.net/10204/1533

Title: Simulating the time-dependent behaviour of excavations in hard rock
Authors: Malan, DF
Keywords: Nuclear waste repositories
Tabular excavation
Fracture zone rheology
Tunnel deformation
Viscoelastic theory
Continuum elasto-viscoplastic modelling
Discontinuum elasto-viscoelastic modelling
Numerical simulation
Issue Date: Oct-2002
Publisher: Springer-Verlag
Citation: Malan, DF. 2002. Simulating the time-dependent behaviour of excavations in hard rock. Rock Mechanics and Rock Engineering, vol. 35(4), pp 225-254
Abstract: Although hard rock is not usually associated with large creep deformation, data collected from the tunnels and stopes of the deep South African gold mines illustrates significant time-dependent behaviour. Apart from application in mining, a better understanding of the time-dependent behaviour of crystalline rock is required to analyse the long term stability of nuclear waste repositories and to design better support for deep civil engineering tunnels in these rock types. To illustrate the subtle problems associated with using viscoelastic theory to simulate the time-dependent behaviour of hard rock, a viscoelastic convergence solution for the incremental enlargement of a tabular excavation is discussed. Data on the time dependent deformation of a tunnel developed in hard rock further illustrates the limitations of the theory, as it is unable to simulate the fracture zone around these excavations. To simulate the rheology of the fracture zone, a continuum viscoplastic approach was developed and implemented in a finite deference code. This proved more successful in modelling the time-dependent closure of stopes and squeezing conditions in hard rock tunnels. A continuum approach, however, has limitations in areas where the squeezing behaviour is dominated by the time-dependent behaviour of prominent discontinuities such as bedding planes. To overcome this problem, a viscoplastic displacement discontinuity technique was developed. This, combined with a tessellation approach, leads to more realistic modelling of the time-dependent behaviour of the fracture zone around excavations.
URI: http://hdl.handle.net/10204/1533
ISSN: 0723-2632
Appears in Collections:Mining and geoscience
General science, engineering & technology

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