Numerical Investigation of Hard Rock Strength and Fracturing under Polyaxial Compression Based on Mogi-Coulomb Failure Criterion

Failure characteristics of rocks under polyaxial compression have been the subject of extensive laboratory testing, although a limited amount of literature is published on the numerical simulation of rock failure under such conditions. The current study was conducted by using a commercially available finite-difference program, FLAC(3D), to model the hard rock strength and fracturing under polyaxial compression. The Mogi-Coulomb criterion, where the relevant parameters can be obtained from conventional triaxial tests, was simulated in the software for realistic reflection of the effects of intermediate principal stress on hard rock fracture characteristics. According to the elastoplastic mechanics, the incremental iterative calculation format of the Mogi-Coulomb strain-softening failure criterion was implemented in the program, and the results were compiled into a dynamically linked library (DLL) based on the program interface of secondary development provided by FLAC(3D). The numerical results of the calculated peak strength were analyzed and compared with previous experimental data for verification of the effectiveness and accuracy of the simulation models. Laboratory tests with consideration of various intermediate principal stresses were also conducted to investigate the hard rock failure modes under polyaxial compression states. The comparison of experimental results with numerical results using both Mogi-Coulomb and Mohr-Coulomb strain-softening models further explained the validity of the former method. The results showed that proper numerical modeling can be considered for simulating hard rock fracturing under polyaxial compression states for complex stress conditions in future studies.