The impact of discontinuities on spalling failure in excavations under high-stress conditions

The Continuum Voronoi Block Model (CVBM), a pseudo-discontinuum modeling technique based on the Finite Element Method, was employed to investigate the impact of discontinuities on spalling phenomena around excavations in rocks under high-stress conditions. The CVBM's ability to produce numerical results consistent with spalling was demonstrated through a case study of the Mine-by tunnel. The results show that the model can explicitly capture the formation of macro-fractures parallel to excavation walls, intact rock slabs, and V-shaped notches. The results of this case study support the application of CVBM for parametric analyses to investigate the role of discontinuities in spalling failure, integrating discrete fracture network (DFN) into the model. The influence of DFN parameters such as dip angle, spacing, persistence, position, and mechanical properties is also evaluated. It was found that discontinuities promote stress relief due to shear, thereby altering spalling damage around the excavation in highly stressed rock. This finding highlights the crucial role of discontinuities in influencing the behavior of excavations under such conditions.