Fracture void structure: implications for flow, transport and deformation

Aydın, Adnan

doi:10.1007/s002549900104

Cited by 15 publications

(13 citation statements)

References 24 publications

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“…5). The overall direction of this crack in the mesh approximates the actual crack direction (Bažant and Oh 1983), as shown in Fig. 5.…”

Section: Smeared-fracture Approachmentioning

confidence: 95%

“…The discrete approach involves some computational disadvantages. For instance, fracturing increases the number of nodes and changes the topological connectivity of the mesh, which creates significant challenges for automating the approach (Suidan and Schnobrich 1973;Bažant and Oh 1983). Even though the smeared-fracture approach does not fully represent the physical nature of a crack, it is an alternative to the discrete-fracture method because it enables the simulation of fracture branching, fracture rotation, and multiple shear and tensile fractures in unpredetermined directions.…”

Section: Smeared-fracture Approachmentioning

confidence: 98%

“…In their proposed smeared-crack approach, Bažant and Oh (1983) proposed modelling the crack band by converting the isotropic elastic moduli of the matrix to an orthotropic one, including a reduction in the stiffness in the direction perpendicular to the fracture. If a crack propagates in an arbitrary direction with respect to mesh lines or follows a curved path, it can be modelled as a zigzag crack band (see Fig.…”

Section: Smeared-fracture Approachmentioning

confidence: 99%

“…The choice of using the discrete-or smeared-fracture approach depends on their computational effectiveness (Bažant and Oh 1983). The discrete approach involves some computational disadvantages.…”

Section: Smeared-fracture Approachmentioning

confidence: 99%

See 3 more Smart Citations

Numerical Modelling of Hydraulic Fracturing in Cohesionless Sand: Validation Against Laboratory Experiments

Taghipoor

Nouri

Chan

2015

Journal of Canadian Petroleum Technology

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In this paper, a new hydraulic-fracturing model is introduced for cohesionless sand, which is also applicable to weak sandstone formations with high permeability and low shear strength. Phenomena such as shear-band development and shear-enhanced permeability are of paramount importance during hydraulic fracturing of cohesionless sand or weak sandstones, which make the fracturing response quite different from what it is conventionally believed to be in competent rocks.The smeared approach in simulating hydraulic fracturing has been implemented in the proposed model within the continuum mechanics framework. Both matrix and fracture flow have been considered in this model. Tensile-and shear-fracture development and their fluid flow were simulated. The cubic law and Touhidi-Baghini's shear-permeability model (Touhidi-Baghini 1998) were used to capture the permeability evolution and to model flow in tensile and shear fractures, respectively. Shear fracturing of geomaterials involves intense localization of deformation and strain softening, which is a discontinuous phenomenon, resulting in mesh dependency of the results in the continuum model. The fracture-energy-regularization method was used in this model to reduce the mesh-size dependency of the energy dissipated during fracture propagation.The smeared-fracture approach has been validated against laboratory hydraulic-fracturing experiments with reasonable agreement. Consistent with the experiments, the results of the numerical model indicate that tensile fractures are formed in a very small area around the injection point despite the application of high injection pressure compared with the minimum boundary stress. It is found that shear fracturing and shear-permeability evolution are the most important mechanisms that influence and control the fracturing response. The dominant fracturing mechanism is found to be governed by the high permeability and low shear strength of the material.

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“…5). The overall direction of this crack in the mesh approximates the actual crack direction (Bažant and Oh 1983), as shown in Fig. 5.…”

Section: Smeared-fracture Approachmentioning

confidence: 95%

Section: Smeared-fracture Approachmentioning

confidence: 98%

Section: Smeared-fracture Approachmentioning

confidence: 99%

Section: Smeared-fracture Approachmentioning

confidence: 99%

See 2 more Smart Citations

Numerical Modelling of Hydraulic Fracturing in Cohesionless Sand: Validation Against Laboratory Experiments

Taghipoor

Nouri

Chan

2015

Journal of Canadian Petroleum Technology

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“…Aydin [7] evaluated the applicability of the cubic law for low flow rates, as well as a wide range of friction and conductivity modification factors based on a number of flow domains.…”

Section: Introductionmentioning

confidence: 99%

On the cubic law and variably saturated flow through discrete open rough-walled discontinuities

Dippenaar

Rooy

2016

International Journal of Rock Mechanics and Mining Sciences

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Highlights• The role of the fractured intermediate vadose zone is becoming increasingly important.• Discontinuity geometry affects flow, most notably due to changes in aperture, roughness and infill.• The applicability of the cubic law is often queried.• Better understanding will contribute to issues of slope and excavation stability and contaminant transport.• Open questions requiring addressing concluded the paper. Abstract:Fracture flow is fairly well documented with the widespread application of, for instance, the cubic law and assumed smooth parallel plate model.Geometrical intricacies such as aperture, roughness and infill do however significantly influence the validity of the cubic law with even its application to smooth parallel systems being contestable. Rock mechanical discontinuity surveys provide valuable information regarding the discontinuity geometry that can likely contribute to the evaluation of flow through individual fractures with variable properties. The hydraulic aperture is available for the transmission of flow, while normal and shear stresses alter discontinuity properties over time. In this, numerous advances have been made to better accommodate deviations of natural discontinuity geometry to that of smooth parallel plates and at partial saturation. The paper addresses these advances and details conditions under which the cubic law, even in local form, fails to adequately estimate the

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Correlation between groundwater flow and deformation in the fractured carbonate Gran Sasso aquifer (INFN underground laboratories, central Italy)

Amoruso

Crescentini

Martino

et al. 2014

Water Resources Research

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The Gran Sasso massif is a carbonate fractured aquifer with a spring discharge of more than 18 m 3 s 21 . The water table has been partially drained by two motorway tunnels and an underground laboratory (UL), located into the core aquifer. Karst features have limited role below the water table, where groundwater flow is mainly regulated by the fracture network. Two paired laser extensometers (BA and BC) recorded ground deformation in the UL. Changes in deformation correlate with the seasonal recharge/discharge cycle of groundwater flow and its long-term changes. Hydrostatic conditions prevail during the recharge phases because of the low permeability of local fractures, favoring compression, and hydraulic gradient increase above the UL. Fast groundwater flow through the high-permeability fault outcropping in the UL can enhance local dilatation for short periods. Spring discharge during exhaustion periods is fed by the low-permeability fracture network, fostering hydrodynamic conditions by hydraulic gradient decrease, diminishing compression and consequently favoring dilatation. Independent support to this conceptual model comes from local tests and a numerical model which highlights the hydromechanical strain effects induced by the hydrological cycle on the jointed rock mass along BA and the role of the hydraulic gradient on the rock mass deformation.

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Fracture void structure: implications for flow, transport and deformation

Cited by 15 publications

References 24 publications

Numerical Modelling of Hydraulic Fracturing in Cohesionless Sand: Validation Against Laboratory Experiments

Numerical Modelling of Hydraulic Fracturing in Cohesionless Sand: Validation Against Laboratory Experiments

On the cubic law and variably saturated flow through discrete open rough-walled discontinuities

Correlation between groundwater flow and deformation in the fractured carbonate Gran Sasso aquifer (INFN underground laboratories, central Italy)

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