Implementation of a Flaw Model to the Fracturing Around a Vertical Shaft

Summary This paper investigates whether a micromechanical model developed to investigate the relation between the basic failure processes at grain-scale and the macroscopic failure pattern can be applied to model the fracturing around large-scale excavations. The simulated fracture pattern around a vertical shaft is compared to the fracturing around a shaft at a depth of 3400 m. The simulations suggest that wedge-shaped zones, called dog-ears, are formed by a progressive splitting-like failure of the rock. The fractures forming these slabs nucleate in the zones subjected to the highest compressive stresses. Both shear and tensile mechanisms are responsible for the fracturing. The dog-ears deepen and widen as spalling continues. Received June 5, 2001; accepted September 24, 2002; Published online January 21, 2003 Acknowledgements The simulations presented in this paper form part of the PhD study of B. Van de Steen at the KULeuven. The authors wish to thank the sponsors of the Deepmine project for the permission to use the information pertaining to the fracturing around the South shaft at Western Deep Levels. Authors' address: André Vervoort, Katholieke Universiteit Leuven, Faculty of Engineering, Department of Civil Engineering, Kasteelpark Arenberg 40, B-3001 Leuven, Belgium; e-mail: andre.vervoort@bwk.kuleuven.ac.be