In this work, a new numerical approach based on the Finite Element Method and an implicit continuum formulation, called Continuum Voronoi Block Model-CVBM, is proposed to represent the fracturing process in hard rocks and also the rupture of underground works with high field stresses. In this model, developed with the RS2 program, the rock mass was simulated by a set of blocks, formed by a Voronoi mosaic, joined at their interfaces by joint elements. Different case studies were represented on a laboratory and field scale. The model proved to be robust on the laboratory scale and described the rock's relevant macro-properties in conventional tests: crack initiation stress, crack damage stress, and peak strength. On a field scale, the model represented the mass deterioration process explicitly, captured the rupture geometry, and the excavations’ displacements. Such results show the CVBM's potential for modelling the behavior of underground works with high field stress.
Underground works may involve excavation in hard rock with high field stresses. These works commonly have a brittle failure process during the excavation steps, known as spalling. The deteriorated rock mass tends to increase in volume due to fracture opening, shear between planes, and geometric incompatibility between blocks. This volume in-crease promotes excessive convergence displacements known as bulking (Diederichs 2007, Kaiser 2016).
Researchers have developed constitutive models to represent this type of failure, based on the concept of initial cohesive strength demobilization followed by subsequent mobilization of frictional strength (Diederichs 2007). These models have been applied to predict the depth of failure in underground excavations caused by spalling. However, the physical processes related to the damage and loss of integrity are not explicitly represented, and bulking is not captured either.
From these limitations, a new numerical approach for rock mass simulation was developed in this work, which is called the Continuum Voronoi Block Model-CVBM. The CVBM is a pseudo-discontinuum modeling technique based on the Finite Element Meth-od-FEM, implemented using the RS2 software. (Rocscience 2019). This model uses Voronoi cells interconnected by Goodman joint elements (Goodman et al. 1968) to represent the rock mass.
