Abstract
Inherent microcrack populations have a significant effect on the fracture behaviour of natural rocks. The present study addresses this topic in numerical simulations of uniaxial tension and three-point bending tests. For this end, a rock fracture model based on multiple intersecting embedded discontinuity finite elements is developed. The inherent (pre-existing) microcrack populations are represented by pre-embedded randomly oriented discontinuity populations. Crack shielding (through spurious locking) is prevented by allowing a new crack to be introduced, upon violation of the Rankine criterion, in an element with an initial crack unfavourably oriented to the loading direction. Rock heterogeneity is accounted for by random clusters of triangular finite elements representing different minerals of granitic numerical rock. Numerical simulations demonstrate the strength lowering effect of initial microcrack populations. This effect is substantially stronger under uniaxial tension, due to the uniform stress state, than in semicircular three-point bending having a non-uniform stress state with a clear local maximum of tensile stress.
Highlights
Rock behaviour under loading is to large extent influenced by heterogeneity
Rock heterogeneity manifests at many scales, ranging from grain level microdefects to geologic macroscale of crustal faults
The finite element formulation of the embedded discontinuity kinematics is based on the enhanced assumed strain concept (EAS) [3, 30, 43, 44]
Summary
Rock behaviour under loading is to large extent influenced by heterogeneity. Rock heterogeneity manifests at many scales, ranging from grain level microdefects (micro- and mesoscale) to geologic macroscale of crustal faults. The particle-based methods are naturally superior to FEM in fracture modelling, due to the underlying discontinuum assumption, and has become a popular choice in numerical modelling of failure processes in brittle materials in general and rock fracture in particular [10, 12, 13, 15, 16, 27, 28, 47, 48, 51] These models are especially attractive, as, in many cases, their rock microstructure description includes explicit grain boundaries and grain boundary cracking. The developed method is validated and applied in numerical simulations of heterogenous granitic rock under uniaxial tension and dynamic three-point bending of semicircular disc
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
