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Openings including their size, shape and distribution in rock play a significant role in the performance of rock related structures. The well-established knowledge in this area can contribute to the engineering practices, for example, underground space design, planning and optimisation in Civil and Mining Engineering and wellbore stability in Drilling Engineering, among others. Thus, understanding the failure mechanism of rock with openings is theoretically and practically meaningful. Laboratory testing on rock or rock-like materials with openings have been studied extensively in the literature, which, however, primarily focuses on the cracks/fractures. In this paper, a comprehensive numerical study on the effect of non-banded openings, i.e., circular, rectangular, and triangular opening, on the rock mechanical behaviour is performed using a hybrid continuum-discrete element method. It is revealed that the proposed simulation method can reproduce reasonably the crack initiation and propagation, and predict well the change of the mechanical behaviour due to the openings. In addition, the influence of the opening shape and opening ratio (=area of opening/specimen area) on the mechanical behaviour is also investigated.

We examine a new continuum micromechanical approach to predicting the macroscopic mechanical responses of Haubourdin chalk under various load conditions. The approach is based on a simple breakage model that accounts for an evolving microstructural degradation through coccosphere crushing with only five physically meaningful parameters and one grading index. The model correlates the intrinsic failure mechanisms including the coccosphere crushing, pore collapse and plastic shearing that are identified by corresponding internal variables within thermodynamic framework. On this basis, numerical predictions of the stresses and strains are examined against their experimental counterparts as well as the results from an existing continuum model. Parametric studies are further conducted to investigate the effect of the model parameters. The favourable agreements in various conventional and complex compression tests indicate a satisfactory performance of the breakage model, highlighting the importance of capturing the microscopic degradation mechanisms when building a constitutive model.

The distinct lattice spring model (DLSM) is extended to modelling soil desiccation cracking by introducing a two-phase bond model. The bond, which comprises a spring bond and water bond, is developed to consider the interaction of the pore pressure with deformation of the soil matrix. A parameter representing soil heterogeneity is introduced to consider the uneven drying during desiccation. The capability of the model is demonstrated through a number of numerical examples, which are in good agreement with the experimental observations. Three significant factors controlling desiccation cracking, which are soil particle size, heterogeneity and boundary conditions, are identified.

A cohesive fracture model considering tension, compression and shear material behaviour is implemented into the hybrid continuum–discrete element method, i.e. Universal Distinct Element Code (UDEC), to simulate possible multiple fracture in soft rocks. The fracture model considers both elastic and inelastic (decomposed to fracture and plastic) displacements. The norm of the effective inelastic displacement is used to control the fracture behaviour. Three numerical examples, including Mode-I, Mode-II and Mixed-mode tests, are conducted to verify the model and its implementation in UDEC. The model is subsequently applied to simulate uniaxial compression and Brazilian disc tests on soft rocks and the results are compared with experimental results. The results indicate that the cohesive fracture model is capable of realistically simulating the combined tensile, shear and mixed-mode failure behaviour applicable to geomaterials.