Dynamic modelling of fault-slip with Barton's shear strength model Atsushi Sainoki n , Hani S. Mitri Department of Mining and Materials Engineering, McGill University, 3450 University Street, Montreal, Quebec, Canada H3A 2A7 article info Article history: Received 19 February 2013 Received in revised form 1 November 2013 Accepted 17 December 2013 Available online 5 March 2014 Keywords: Dynamic analysis Fault slip Barton's shear strength model Seismic source parameters Peak particle velocity abstract Barton's shear strength model has been incorporated into the FLAC3D code as a ubiquitous joint model using the plastic flow rule, to analyze the potential effect of fault-slip bursts on mine openings. Comparison of the incorporated model with the classical Mohr–Coulomb model is conducted through a case study of a primary fault that is parallel to a steeply dipping tabular ore deposit, which is mined out by the sublevel stoping method. Based on the results obtained from the numerical analyses, seismic source parameters are calculated and compared for each case. The results show that faults having rough surfaces tend to cause much larger seismic events than faults with smooth surfaces. In addition, parametrical study with respect to fault-surface roughness shows that seismic moment and radiated energy significantly vary with the fault-surface roughness and the seismic moment does not necessarily correlate with the radiated energy. Peak particle velocity excited by seismic waves arising from the simulated fault-slips is also examined. It is found out from the results that peak particle velocity is strongly dependent upon the fault surface roughness and has a correlation with the radiated energy, but not with seismic moment. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction Fault-slip burst caused by mining activities is one of the most dangerous phenomena that occur in underground hard rock mines. According to case studies conducted by Blake and Hedley [1], fault-slip burst that occurred at Wright-Hargreaves Mine recorded a magnitude of 4.2 and caused significant damage to mine openings ranging from 1143 m to 777 m below the ground surface. The authors indicated that the triggering mechanism of fault-slip bursts is a reduction in the clamping force acting on the fault, so that there are no warnings related to fault-slip bursts. Hence, predicting the fault-slip burst is quite challenging in mine sites, where complicated geological structures and stress regimes exist. To date, many attempts in examining the relation between mining activities and the occurrence of the fault-slip bursts have been made. Castro and Carter [2] investigated various types of case studies that possibly lead to fault-slip bursts due to the effect of mining activities, such as the unclamping of normal stress acting on faults and stress rotation induced by the extraction of stopes. Hofmann and Scheepers [3] simulated fault-slip area with Mohr– Coulomb failure criterion by considering the reduction in the cohesive strength of a fault due to rupture so that the fault-slip area corresponds with that estimated from recorded data. Sainoki and Mitri [4] modelled the dynamic behaviour of fault-slip induced by the extraction of stopes and estimated seismic source parameters of the fault-slip. While modelling of the fault-slip in mining context has been attempted as shown above, the classical Mohr–Coulomb criterion has been mainly used for the shear strength model representing the resistance to shear stresses acting on the faults because of its simplicity to incorporate into the procedure for modelling the fault- slip. However, fault surfaces observed in mine sites are never planar [5] due to a variety of factors which influence fault formation, such as rockmass fabrics, in-situ stresses, and geological structures. Dieterich and Kilgore [6] indicated that asperity of the surfaces of faults depends on the net slip that the faults experience and that asperity controls friction as well as slip type and velocity. Hence, it is evident that the use of Mohr–Coulomb criterion as the shear strength model of the faults could lead to inaccurate results when fault-surface roughness is large enough that the surface cannot be regarded as planar. To take into account the asperity of the fault or joint surfaces, many shear strength models have been proposed theoretically and experimentally. Barton [7] proposed an empirical shear strength model taking the surface roughness into considera- tion, based on the experimental results from direct shear tests performed on artificial rough tension joints of brittle model material. Saeb [8,9] modified Ladanyi and Archambault's shear strength model that considers the angle of asperity dependence upon the ratio of normal stress to uniaxial compressive stress. Indraratna, Welideniya [10] proposed a shear strength model that Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/ijrmms International Journal of Rock Mechanics & Mining Sciences http://dx.doi.org/10.1016/j.ijrmms.2013.12.023 1365-1609 & 2014 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ1 514 549 8466; fax: þ1 514 398 7396. E-mail address: atsushi.sainoki@mail.mcgill.ca (A. Sainoki). International Journal of Rock Mechanics & Mining Sciences 67 (2014) 155–163