Characterisation and modelling of natural fracture networks: geometry, geomechanics and fluid flow

Natural fractures are ubiquitous in crustal rocks and often dominate the bulk properties of geological formations. The development of numerical tools to model the geometry, geomechanics and fluid flow behaviour of natural fracture networks is a challenging issue which is relevant to many rock engineering applications. The thesis first presents a study of the statistics and tectonism of a multiscale fracture system in limestone, from which the complexity of natural fractures is illustrated with respect to hierarchical topologies and underlying mechanisms. To simulate the geomechanical behaviour of rock masses embedded with natural fractures, the finite-discrete element method (FEMDEM) is integrated with a joint constitutive model (JCM) to solve the solid mechanics problems of such intricate discontinuity systems explicitly represented by discrete fracture network (DFN) models. This computational formulation can calculate the stress/strain fields of the rock matrix, capture the mechanical interactions of discrete rock blocks, characterise the non-linear deformation of rough fractures and mimic the propagation of new cracks driven by stress concentrations. The developed simulation tool is used to derive the aperture distribution of various fracture networks under different geomechanical conditions, based on which the stress-dependent fluid flow is further analysed. A novel upscaling approach to fracture network models is developed to evaluate the scaling of the equivalent permeability of fractured rocks under in-situ stresses. The combined JCM-FEMDEM model is further applied to simulate the progressive rock mass failure around an underground excavation in a crystalline rock with pre-existing discontinuities. The scope of this thesis covers the scenarios of both two-dimensional (2D) and three-dimensional (3D) fracture networks with pre-existing natural fractures and stress-induced new cracks. The research findings demonstrate the importance of integrating explicit DFN representations and conducting geomechanical computations for more meaningful assessments of the hydromechanical behaviour of naturally fractured rocks.Open Acces

Deriving Global Material Properties of a Microscopically Heterogeneous Medium - Computational Homogenisation and Opportunities in Visualisation

In order to derive the overall mechanical response of a microscopically material body, both the theoretical and the numerical framework of multi scale consideration coined as computational homogenisation is presented. Instead of resolving the actual heterogeneous microstructure in all detail for its simulation, representative micro elements are considered which provide the material properties for the coarse or rather scale. This procedure allows for a smaller and less inexpensive computation. However both the chance and challenge of visualising the decisive features arise on two scales

MS FT-2-2 7 Orthogonal polynomials and quadrature: Theory, computation, and applications

Quadrature rules find many applications in science and engineering. Their analysis is a classical area of applied mathematics and continues to attract considerable attention. This seminar brings together speakers with expertise in a large variety of quadrature rules. It is the aim of the seminar to provide an overview of recent developments in the analysis of quadrature rules. The computation of error estimates and novel applications also are described

Generalized averaged Gaussian quadrature and applications

A simple numerical method for constructing the optimal generalized averaged Gaussian quadrature formulas will be presented. These formulas exist in many cases in which real positive GaussKronrod formulas do not exist, and can be used as an adequate alternative in order to estimate the error of a Gaussian rule. We also investigate the conditions under which the optimal averaged Gaussian quadrature formulas and their truncated variants are internal

Development of the high throughput mammalian PIG-A gene mutation assay in vitro.

The field of genetic toxicology has recently undergone reform which has limited or banned the use of animal models within a number of different industries (cosmetics). Consequently, greater emphasis has been placed on developing novel, highly sensitive, in vitro test systems which can generate robust data to aid regulatory hazard and risk assessment.The main aims of this project were i) to develop a highly sensitive and specific, high throughput mammalian in vitro PIG-A gene mutation assay to enable quantitative dose response modelling and further investigate the potential use of in vitro data within human health assessment, ii) Investigate the genotype to phenotype relationship, a potentially delaying step within future OECD guideline drafting for the current in-vivo Pig-a mutation assay and iii) help develop and optimise a preliminary comprehensive human PIG-A bio­monitoring platform.During in-vitro and ex-vivo PIG-A assay development, flow cytometry was the fundamental technique utilised. Multiple additional laser excitation platforms were evaluated for use, including Amnis ImageStream ™ and laser scanning confocal. Proteomic as well as genomic techniques were used during the supplementary investigations surrounding assay development, with microbiological groundings throughout.The finalised in-vitro assay protocol was established within human, metabolically active, MCL-5 cells. Using the refined assay design, proof of principle experimentations were able to show the potential for future quantitative work and the general promise with this novel approach. The genotype to phenotype relationship validation is currently still on-going following the preliminary work described herein and recent publications. The ex-vivo human PIG-A assay platforms were shown to require further optimisation in terms of sensitivity, excluding red blood cells, but showed good aptitude for future use.Currently it looks promising that further refinement could lead to a comprehensive high content, high-throughput assay system with the potential to be used within future hazard and risk assessmen