A note on brittle crack growth in compression

Brace, W. F.; Bombolakis, E. G.

doi:10.1029/jz068i012p03709

Cited by 777 publications

(245 citation statements)

References 5 publications

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“…Conversely, other activated flaws will close and ridge, which strengthen the pack. In the laboratory, as local stress concentrates at the tips of the flaw, wing cracks may be formed that will relax the stress in the manner described by Brace and Bombolakis [1963], Nemat-Nasser and Horii [1982], and Ashby and Hallam [1986]. In this model, intensified tension, as noted (Figure 8b), leads to failure and the formation of oriented flaws in adjacent grid cells.…”

Section: Propagation Of Damagementioning

confidence: 90%

On modeling the anisotropic failure and flow of flawed sea ice

Hibler¹,

Schulson²

2000

J. Geophys. Res.

119

131

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Abstract. The failure and flow of sea ice on scales small and large is characterized by the propagation of oriented leads and cracks. In this paper a theory for the dynamical treatment of anisotropic oriented flaws in sea ice is developed and used to examine the interaction of these oriented flaws under idealized stress forcing. The essential idea of the theory is to take one or more oriented weak leads imbedded in thick ice. A constitutive law for both the thin and thick ice is taken to be similar to laboratory observations, which are consistent with Mohr Coulomb-like failure. Application of normal continuum mechanics boundary conditions leads to anisotropic flow and failure characteristics of this anisotropic composite under both near-and far-field forcing. The local failure characteristics show that there is a preferred orientation for failure with the intersection between "leads" increasing as confinement increases. For spatially separated interacting flaws the theory predicts a preference for the weakening of flaws in a narrow range of angles of-10ø-20 ø relative to the principal far-field stress. Imbedding isolated flaws leads to simulated damage directions consistent with local failure characteristics. In the case where the ice is considered to have available flaws in all directions, fracture propagation is found to proceed by picking out oriented flaws alternating in direction along large-scale damage strikes with individual flaw alignments of -20 ø relative to far-field principal stresses. The mechanisms responsible for these results and how this anisotropic sea ice rheology might be implemented in current dynamic/thermodynamic sea ice models are discussed. IntroductionThe failure and flow of sea ice on scales both small and large are characterized by the propagation of oriented leads and cracks. These patterns typically nucleate from local imperfections and flaws. Understanding and modeling the physical processes responsible for these oriented patterns is especially relevant to describing the mechanical characteristics of geophysical-scale sea ice under deformation and is relevant to the role of sea ice in global climate change and in ice forecasting applications.As Since we believe these oriented leads and slip lines to nucleate from local imperfections that are themselves oriented, an anisotropic description of individual elements of the ice is clearly critical in describing the aggregate behavior of this composite system. In much work on the small scale, anisotropic behavior has been described by fixed friction models of cracks [see, e.g., Schulson and Nickolayev, 1995]. This concept has also been proposed in modified form by Coon et al. [1992, 1998] as the foundation of an anisotropic sea ice model on the geophysical scale. In the theoretical model proposed here a different approach is used. Specifically, rather than assume a fixed lead orientation model for leads, we assume that both thick ice and thinner ice in oriented leads or flaws have a rheology similar in form to that observed for columnar ...

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Section: Propagation Of Damagementioning

confidence: 90%

On modeling the anisotropic failure and flow of flawed sea ice

Hibler¹,

Schulson²

2000

J. Geophys. Res.

119

131

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“…A simple 2D sliding crack model has first been proposed by Brace and Bombolakis [89]. According to this, present cracks in any brittle material extend along a curved path that eventually becomes parallel to the compression axis.…”

Section: Microcrack Based Sliding Crack Modelsmentioning

confidence: 99%

An Alternative to Conventional Rock Fragmentation Methods Using SCDA: A Review

2016

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Global energy and material consumption are expected to rise in exponential proportions during the next few decades, generating huge demands for deep earth energy (oil/gas) recovery and mineral processing. Under such circumstances, the continuation of existing methods in rock fragmentation in such applications is questionable due to the proven adverse environmental impacts associated with them. In this regard; the possibility of using more environmentally friendly options as Soundless Chemical Demolition Agents (SCDAs) play a vital role in replacing harmful conventional rock fragmentation techniques for gas; oil and mineral recovery. This study reviews up to date research on soundless cracking demolition agent (SCDA) application on rock fracturing including its limitations and strengths, possible applications in the petroleum industry and the possibility of using existing rock fragmentation models for SCDA-based rock fragmentation; also known as fracking. Though the expansive properties of SCDAs are currently used in some demolition works, the poor usage guidelines available reflect the insufficient research carried out on its material's behavior. SCDA is a cementitious powdery substance with quicklime (CaO) as its primary ingredient that expands upon contact with water; which results in a huge expansive pressure if this CaO hydration reaction occurs in a confined condition. So, the mechanism can be used for rock fragmentation by injecting the SCDA into boreholes of a rock mass; where the resulting expansive pressure is sufficient to create an effective fracture network in the confined rock mass around the borehole. This expansive pressure development, however, dependent on many factors, where formation water content creates a negative influence on this due to required greater degree of hydration under greater water contents and temperature creates a positive influence by accelerating the reaction. Having a precise understanding of the fracture propagation mechanisms when using SCDA is important due to the formation of complex fracture networks in rocks. Several models can be found in the literature based on the tangential and radial stresses acting on a rock mass surrounding an SCDA charged borehole. Those fracture models with quasi-static fracturing mechanism that occurs in Mode I type tensile failure show compatibility with SCDA fracturing mechanisms. The effect of borehole diameter, spacing and the arrangement on expansive pressure generation and corresponding fracture network generation is important in the SCDA fracturing process and effective handling of them would pave the way to creating an optimum fracture network in a targeted rock formation. SCDA has many potential applications in unconventional gas and oil recovery and in-situ mining in mineral processing. However, effective utilization of SCDA in such application needs much extensive research on the performance of SCDA with respect to its potential applications, particularly when considering unique issues arising in using SCDA in different ...

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“…This fact is emphasized by observing that samples dilate as peak stress is approached [Brace et al, 1966]. Direct observation has also shown that shear cracks cannot propagate in their own plane [Brace and Bombolakis, 1963;Horii and NematNasser, 1985]. Therefore the eventual failure of the sample must occur by interaction of the tensile cracks to form a macro shear fault.…”

Section: Introductionmentioning

confidence: 99%

Micromechanical modeling of cracking and failure in brittle rocks

Hazzard¹,

Young²,

Maxwell³

2000

J. Geophys. Res.

240

108

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Abstract. Dynamic micromechanical models are used to analyze crack nucleation and propagation in brittle rock. Models of rock are created by bonding together thousands of individual particles at points of contact. The feasibility of using these bonded particle models to reproduce rock mechanical behavior is explored by comparing model behavior to results from actual laboratory tests on different rock types. The behavior of two granite models are examined in detail to study cracking and failure patterns that occur during compressional loading. Because discontinuum models are being used, the rock models are free to crack and break apart under stress, such that the micromechanics of cracking can be examined. Stress waves are allowed to propagate outward from each crack, and it is shown that these dynamic waves significantly affect the rock behavior. As the peak stress in the modeled rock is approached and many of the bonds are close to breaking, a passing wave from a nearby crack is sufficient to break more bonds. This causes clusters of cracks to be created, and then eventual macroscopic shear failure occurs as these clusters connect to bisect the sample. The failure patterns observed in the granite models are similar to those observed in actual laboratory tests. . These studies show that in sandstones, shear localization usually does not develop until after the peak stress has been reached. Most of the cracking occurring before the peak stress appears to be intergranular (between grains). This is a departure from low-porosity crystalline rocks (granite) in which many of the cracks are intragranular [Tapponnier and Brace, 1976]. In sandstones it appears that most cracking occurs along grain boundaries, either by widening of preexisting microcracks or by shear rupturing of the cement at the grain contacts caused by rotation and slip of the grains. The high level of acoustic emissions (AE) recorded during dilation gives evidence that this second process is occurring. 16,683

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A note on brittle crack growth in compression

Cited by 777 publications

References 5 publications

On modeling the anisotropic failure and flow of flawed sea ice

On modeling the anisotropic failure and flow of flawed sea ice

An Alternative to Conventional Rock Fragmentation Methods Using SCDA: A Review

Micromechanical modeling of cracking and failure in brittle rocks

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