Using PFC~(2D) to simulate the shear behaviour of joints in hard crystalline rock

摘要

Significant uncertainties remain regarding the assessment of the peak shear strength of rock joints. In recent years, ParticleFlow Code (PFC) has been used to simulate shear tests of rock joints. Although previous studies showed PFC’s capabilityto simulate rock joint shear behaviour, it is uncertain how different parameters in PFC should be combined to realisticallycapture roughness and strength of asperities in contact of actual rock joints. Under low normal stresses, the shear behaviourof well-mated hard crystalline joints is governed by the interaction between asperities of some tenths of a millimetre. Thispaper investigates the capability of PFC~(2D)to realistically simulate the peak shear strength of hard crystalline rock jointsunder different constant normal stress magnitudes. The simulated two-dimensional profiles were selected from the digitisedjoint surface obtained with optical scanning measurements. To realistically capture surface roughness and asperity strengthin PFC~(2D),different values of joint segment length, particle resolution per segment, and bond strength between particles werestudied and calibrated while taking into account the laboratory observations. The results of the numerical simulations in thePFC~(2D)environment show that the simulated peak shear strength using the profile containing the steepest asperity is in goodagreement with that measured in the laboratory. The joint profile needs to be represented by both a magnitude of segmentlength that captures the grain size, and at least two particles per segment. The bond strength calibration needs to account forboth asperity size and the number of particles in contact during shearing.