Journal ArticleDOI
Joint pattern development: Effects of subcritical crack growth and mechanical crack interaction
TLDR
In this paper, a subcritical fracture growth model is used to generate equilibrium crack geometries, where fracture length distributions and spacing are modeled as proportional to the n-th power of the mode I stress intensity.Abstract:
Fracture networks are examined in the light of subcritical crack growth theory. Examples of equilibrium crack geometries are generated using a fracture mechanics model that explicitly tracks the propagation of multiple fractures. It is determined that propagation velocity as modeled using a subcritical fracture growth law exerts a controlling influence on fracture length distributions and spacing. Velocity is modeled as proportional to the n-th power of the mode I stress intensity. Numerous, closely spaced, similar length fractures result for n=1, with many en echelon arrays forming due to fracture interaction. Increasing the value of n results in the growth of fewer fractures that are more widely spaced. Fractures tend to cluster in narrow zones, with limited fracture growth in the intervening areas. The spacing between zones is controlled by the stress shielding effects of longer fractures on shorter ones. The amount of time required for fracture pattern development is also influenced by the subcritical velocity exponent, n. At low n, patterns take seconds to minutes to develop, while patterns generated at higher n can require hundreds of years or more.read more
Citations
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Natural fractures in shale: A review and new observations
TL;DR: In this article, the authors present new core and outcrop data from 18 shale plays that reveal common types of shale fractures and their mineralization, orientation, and size patterns, and identify a need for further work in this field and on the role of natural fractures generally.
Journal ArticleDOI
Characteristics and origins of coal cleat: A review
TL;DR: Cleats are natural opening-mode fractures in coal beds and account for most of the permeability and much of the porosity of coalbed gas reservoirs and can have a significant effect on the success of engineering procedures such as cavity stimulations as discussed by the authors.
Journal ArticleDOI
The use of discrete fracture networks for modelling coupled geomechanical and hydrological behaviour of fractured rocks
TL;DR: In this paper, the authors present a discussion of the state-of-the-art on the use of discrete fracture networks (DFNs) for modelling geometrical characteristics, geomechanical evolution and hydromechanical (HM) behaviour of natural fracture networks in rock.
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Natural fracture characterization in tight gas sandstones: Integrating mechanics and diagenesis
TL;DR: In this paper, Poroelastic stress calculations combined with fracture mechanics criteria show that it is possible to sustain opening-mode fracture growth with sublithostatic pore pressure without associated or preemptive shear failure.
Journal ArticleDOI
Hydrothermal breccias in vein-type ore deposits: A review of mechanisms, morphology and size distribution
TL;DR: A review of the main brecciation processes occurring in hydrothermal vein-type deposits allows for the discrimination between chemical and physical mechanisms, including tectonic comminution, wear abrasion, two types of fluid-assisted breccia (hydraulic and critical), volume expansion or reduction, impact and collapse.
References
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Journal ArticleDOI
Elastic moduli of a cracked solid
TL;DR: In this paper, a self-consistent method for the elastic moduli of bodies containing randomly distributed flat cracks, with or without fluid in their interiors, is proposed and general concepts are outlined for arbitrary cracks and explicit derivations together with numerical results are given.
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Slightly curved or kinked cracks
Brian Cotterell,James R. Rice +1 more
TL;DR: In this paper, a solution for the elastic stress intensity factors at the tip of a slightly curved or kinked two-dimensional crack is presented for the deviation of the crack surface from a straight line and is carried out by perturbation procedures analogous to those of Banichuk [1] and Goldstein and Salganik [2, 3].
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Dilatancy in the Fracture of Crystalline Rocks
TL;DR: In this paper, the authors measured volume changes of a granite, a marble, and an aplite during deformation in triaxial compression at confining pressure of as much as 8 kb.
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Subcritical crack growth in geological materials
TL;DR: A review of the experimental data on subcritical crack growth in geological materials is presented in this article, where the main parameters describing subcritical cracking growth are the critical stress intensity factor Kc, the sub critical crack growth limit Ko, and the relationship between Ko and Kc.
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Progress in understanding jointing over the past century
David Pollard,Atilla Aydin +1 more
TL;DR: Theoretical methods have been developed to study the evolution of joint sets and the mechanical response of a jointed rock mass to tectonic loading in the Earth's crust as mentioned in this paper.