Cored samples are used at different design stages of underground excavations to determine the laboratory properties of intact rocks, including the Unconfined Compressive Strength (UCS) and Young’s modulus (E). Previous research has revealed that when cores are retrieved from deep and high-stress environments, they may experience damage in the form of microcracks, which can affect their laboratory properties. In this research, the influence of coring stress path on damage formation and associated strength degradation is investigated using an advanced numerical program based on the hybrid Finite-Discrete Element Method (FDEM). For this purpose, two-dimensional (2D) FDEM models of laboratory specimens were generated with triangular elements representing grains. Models were then calibrated to the laboratory properties of undamaged Lac de Bonnet (LdB) granite, the typical host rock at the Underground Research Laboratory (URL) in Manitoba, Canada. The laboratory properties used for model calibration include the unconfined and confined compressive strengths, as well as the direct and indirect tensile strengths. In the next step, the coring stress path obtained from a 3D elastic continuum model for a vertical borehole at the 420 Level of the URL was applied to the calibrated 2D model. This resulted in the formation of microcracks, oriented parallel to the major principal stress direction. The damaged numerical specimen was then subjected to uniaxial loading until failure. The results of the unconfined compression test simulation indicate that the damaged specimen exhibits lower peak strength and deformation modulus compared to the undamaged specimen. It is concluded that the hybrid FDEM employed in this research can replicate the unloading-induced brittle damage mechanisms, including crack initiation and crack opening during core drilling, as well as crack closure during uniaxial loading. Furthermore, the FDEM can simulate associated changes in the laboratory properties of hard, brittle rocks. This research addresses the need for more reliable design parameters for underground excavations in the mining, civil, nuclear waste, and petroleum industries. Future work involves investigating the influence of grain-scale geometric and stiffness heterogeneities on drilling-induced core damage. This will be achieved by generating homogeneous (consisting of one mineral type) and heterogeneous (consisting of four mineral types) grain-based FDEM models of LdB granite laboratory specimens utilizing Voronoi blocks.

The Callovo-Oxfordian (COx) claystone is a quasi-brittle anisotropic sedimentary rock considered in France as a potential host rock suitable for deep geological repository of nuclear wastes. Firstly, the objective is to reproduce localised failure and cracking mechanisms in shearing and opening modes to characterise the material deformation and fracturing observed at macroscale. Secondly, this work investigates the effects of the inherent anisotropic nature of the COx claystone on the macroscopic shear strength. A 3D numerical model based on the distinct element method has been developed to reproduce the main features of its mechanical behaviour under triaxial loading conditions, considering its inherent anisotropic nature through morphological aspects. A series of triaxial loading tests was simulated using 3DEC to reproduce the experimental data obtained on the COx claystone. The proposed distinct element model is able to well reproduce rock anisotropic behaviour and the influence of confining pressure on the rock failure mode.

Simplified analytical evaluations of chemical explosives such as TNT, ANFO, PETN, and emulsion reveal notable distinctions when compared to cylinder expansion experiments and equation of state (EOS) data. The reliability of simplified analytical methodologies in determining the reaction zone of these explosives is questionable. In contrast, employing computational methods has become commonplace to achieve a more precise description of detonation products. This paper aims to delve into the behavior of chemical explosives through the application of combined Eulerian-Lagrangian smoothed particle hydrodynamics (ELSPH). The objective is to derive parameter sets for these explosives aligned with the JWL (Jones-Wilkins-Lee) equation of state (EOS). This approach not only provides a pathway to characterize explosives used in rock blasting but also proves valuable in compensating for the inherent limitations in experimental measurements. It accommodates variations in explosive properties across different industrial batches of detonation products, acknowledging the challenges posed by restricted accuracy in experimental measurements.

This work is an attempt to improve the fundamental understanding of the role of the fracture network in rock mass failure and in estimating rock mass effective strength. In most rock masses, the ubiquitous presence of natural fractures reduces the deformation modulus and strength compared to the properties of intact rock. The relationships of rock classification systems, such as the Geological Strength Index (GSI), take this effect into account only qualitatively. Their predictive capacity is very limited especially when extrapolation to scale and anisotropy aspects are important. A description of the fracture network relevant to strength includes the fracture density, the preferential orientation sets but also the multiscale organization of fracture sizes, generally described by power-law models and scaling exponents. All these parameters are keys to quantify rock mass properties, as well as their scaling behaviour, in terms of connectivity, flow and transport capacity and mechanical modulus properties. Previous work has shown how the rock mass modulus can be related to geometrical indicators suitable for multi-scale fracture networks. We pursue this work and further use the Discrete Fracture Network (DFN) based approach for modelling the rock mass. It is combined with numerical models developed in the software 3DEC® to generate numerous synthetic rock mass samples on which UCS and tensile mechanical tests are performed. In these numerical simulations, cracks appear in the rock surrounding the fractures as the deformation increases until peak stress is reached. Building on the established relationship between DFN percolation parameter and rock mass elastic modulus and considering the correlation between the latter and the effective strength, we develop indicators to quantify the evolution of damage and DFN properties, between the initial and the peak stress state, and to relate the ratio between the strength of the intact rock and the strength of the effective rock to the geometric and mechanical variables characteristic of fracture networks.

Located on the border between Zambia and Zimbabwe, the Kariba Dam was constructed on the Zambezi river between 1956 - 1959, creating the largest man-made lake by reser-voir volume. Heavy spillages have progressively scoured an 80 m deep plunge pool, im-mediately downstream of the dam, threatening its foundations. Given the importance of the dam, the decision to undertake the Kariba Dam Rehabilitation Project (KDRP) to en-sure its longevity, long term efficient operation and its continued contribution to energy security and economic prosperity in the region was made. Under the KDRP, the plunge pool reshaping works seek to reshape the plunge pool, in-creasing the basin energy dissipative capacity to reduce the backward scour towards the dam foundations. The nature of the project, with an open-pit excavation at the foot of an existing dam in full operation is unprecedented and constitutes a real rock engineering challenge. This paper highlights the design activities carried out during the works.

Rock-Socketed Piles (RSPs) are a common type of deep foundation used to support heavy concentrated loads from the superstructure, and to transfer them to deeper hard rocks. Due to its worldwide applications, several works have been focused on the study of the load and shaft resistance – settlement response when the RPS is axially loaded, using field load tests, exper-imental small-scale physical tests and numerical models. However, despite previous efforts, an in-depth analysis of the stresses mobilized at the pile-rock interface (PRI) is still needed. This work aims to provide a contribution in that direction, using a 3D numerical model of axially loaded rough RSPs developed with the Distinct Element Method (DEM). Then, the stress path and the behavior at the pile-rock interface (PRI) of RSP are analyzed. Finally, DEM results are compared with results obtained with the cavity expansion theory proposed by others.