This paper presents an application of two shear strength models, namely Barton's shear strength model and modified Ladanyi and Archambault's model, to dynamic modelling of fault-slip that occurs in deep underground mines. First, incorporating the shear strength models into FLAC3D as ubiquitous joint models using plastic flow rule is demonstrated. Subsequently, in order to compare the newly incorporated shear strength models with the classical Mohr-Coulomb model, static and dynamic analyses are carried out for a case study of a primary fault that is parallel to a steeply dipping tabular ore deposit, which is mined out by sublevel stoping method. The comparison shows that seismic moment and energy released during the fault-slip computed for the newly implemented shear strength models are much greater than those for Mohr-Coulomb model. This result implies that faults with undulating surfaces could lead to large seismic events and severe damage to mine openings, compared with those with smooth surfaces.
Fault slip induced by stress re-distribution due to mining activities in deep underground mines could cause large seismic events and inflict severe damage to nearby openings. For better understanding of a mechanism of the fault slip, many efforts have been made (Alber et al. 2011, Castro et al. 2009, Hofmann & Scheepers 2011). Through the research, a relation between the occurrence of fault slip and mining activities has been studied. However, the classical Mohr-Coulomb criterion is generally used for simulating the fault slip because of simplicity of the equation and limitations of commercial software used for the analysis.
Rock joints and faults encountered in underground mines are basically undulating and curved (Wallace & Morris 1986), and behaviour of the undulating joints is significantly different from planar ones, especially with respect to peak shear strength. Since the middle of the last century, many shear strength models for non-planar joints have been developed (Barton 1973, Barton et al. 1985, Ladanyi & Archambault 1970, Indraratna et al. 2005, Newland & Allely 1957). The shear strength models have taken into account joint surface roughness, an angle of asperities, an effect of normal stress acting on a joint on dilatancy, and infill materials, resulting in a large difference from the peak shear strength derived from Mohr-Coulomb criterion.
For these reasons, simulating fault slip that occurs in deep underground mines necessitates consideration of the undulation of joint surfaces. The present study examines the effect of joint-surface roughness on a magnitude and energy of fault-slip by conducting static and dynamic analyses with a numerical model based on a case study.