M.C. Villeneuve

Effects of Grain Scale Heterogeneity on Rock Strength and the Chipping Process

AbstractHeterogeneity is an important factor controlling fracture initiation, accumulation, and propagation within polycrystalline rock. Internal spatial variability in terms of mineralogy, grain size, and anisotropy affect the yielding process. To investigate these factors, a texture-generating algorithm integrated within a numerical model was developed to create realistic rock analogs and provide user control over geological characteristics including mineral type, grain size, and anisotropic crystal shape. A mineral-specific constitutive model was created and calibrated using published values and real laboratory strength values. Brazilian tensile strength and unconfined compressive strength (UCS) model tests were developed using the finite-difference modeling software FLAC to perform parametric analysis of a series of geological characteristics. The results show that the methodology is capable of realistically reproducing damage propagation and failure behavior similar to that observed during laboratory...

Engineering Geology Education in Australasia

Recent geohazard events, continued urban, infrastructure and resource development, and climate change in Australasia and internationally highlight the need for engineering geologists. In Australasia engineering geology is gaining recognition as a distinct profession that provides the link between engineering and geology. An important aspect of engineering geology training is through tertiary education aimed at providing the industry with work-ready graduates who are knowledgeable in the principles of engineering geology. This is achieved through a variety of programs, each with a different approach and level of proficiency upon graduation. The most common format is a single, introductory course offered in the final year of a Bachelor of Science (B.Sc.) in geology (or geoscience, earth science, etc.) available at many tertiary institutes that have a geology program. Also common are the several postgraduate courses that either build upon introductory undergraduate courses, or are stand-alone courses that form part of a taught postgraduate degree (B.Sc. (Honours), postgraduate diploma or Masters) or are combined with a thesis focused on research in engineering geology (M.Sc.). There is one postgraduate program with a comprehensive curriculum specifically aimed at educating and training engineering geologists through coursework and dissertation. Finally, engineering geology education and training is offered through geotechnical professional societies. The courses vary between institutions based on the structure of the programs and the expertise of the academic staff. This paper provides an overview of the types of courses, their learning outcomes, pedagogy, and how they form the different programs addressing engineering geology education in Australasia.

Geomechanical Characterisation of Hard Rocks for Disc Cutting in Deep Tunnels

The disc cutting process for TBM excavation is dependent on the ability of the discs to initiate and propagate fractures into the tunnel face. At any depth, the geomechanical characteristics of the rock will determine how efficiently the fracture initiation and propagation processes occur. In deep tunnels the stresses induced at the tunnel boundary can lead to stress-induced failure mechanisms such as spalling and bursting. This paper examines the impact of geomechanical characteristics in combination with induced stresses at the tunnel face on the disc cutting process. TBM performance data and tunnel face maps were combined with mineralogy, grain size and fabric for deep tunnels in granitic and foliated massive rocks to determine how induced stresses enhance or hinder the fracture initiation and propagation processes. The impact of the induced stress varies with different geomechanical characteristics depending on the orientation and relative magnitudes of the stresses. In addition, stress rotation and relaxation ahead of the face can lead to stress-induced fracture creation at the face, which acts to precondition the rock prior to the cutters excavating. These results show that the sensitivity of different rock types to stress-related enhancement or hindrance of disc cutting must be taken into account for deep tunneling projects and are used to propose a geomechanical characterisation approach to identify potential for increased or reduced disc cutting efficiency in deep tunnels.