Joint aperture and roughness in the prediction of flow and groutability of rock masses

Barton, Nick; Quadros, Eda

doi:10.1016/s1365-1609(97)00081-6

Cited by 74 publications

(21 citation statements)

References 5 publications

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“…JRC is the joint roughness coefficient, with JRC = 2.5 indicating a very smooth fracture, whereas a fracture with JRC = 20 is extremely rough (Barton and De Quadros, 1997). In our models, we use JRC = 15, assuming relatively rough fractures.…”

Section: Fracture Propertiesmentioning

confidence: 99%

Numerical modeling of fluid effects on seismic properties of fractured magmatic geothermal reservoirs

et al. 2017

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Abstract. Seismic investigations of geothermal reservoirs over the last 20 years have sought to interpret the resulting tomograms and reflection images in terms of the degree of reservoir fracturing and fluid content. Since the former provides the pathways and the latter acts as the medium for transporting geothermal energy, such information is needed to evaluate the quality of the reservoir. In conventional rock physics-based interpretations, this hydro-mechanical information is approximated from seismic velocities computed at the low-frequency (field-based) and high-frequency (labbased) limits. In this paper, we demonstrate how seismic properties of fluid-filled, fractured reservoirs can be modeled over the full frequency spectrum using a numerical simulation technique which has become popular in recent years. This technique is based on Biot's theory of poroelasticity and enables the modeling of the seismic velocity dispersion and the frequency dependent seismic attenuation due to waveinduced fluid flow. These properties are sensitive to key parameters such as the hydraulic permeability of fractures as well as the compressibility and viscosity of the pore fluids. Applying the poroelastic modeling technique to the specific case of a magmatic geothermal system under stress due to the weight of the overlying rocks requires careful parameterization of the model. This includes consideration of the diversity of rock types occurring in the magmatic system and examination of the confining-pressure dependency of each input parameter. After the evaluation of all input parameters, we use our modeling technique to determine the seismic attenuation factors and phase velocities of a rock containing a complex interconnected fracture network, whose geometry is based on a fractured geothermal reservoir in Iceland. Our results indicate that in a magmatic geothermal reservoir the overall seismic velocity structure mainly reflects the lithological heterogeneity of the system, whereas indicators for reservoir permeability and fluid content are deducible from the magnitude of seismic attenuation and the critical frequency at which the peak of attenuation and maximum velocity dispersion occur. The study demonstrates how numerical modeling provides a valuable tool to overcome interpretation ambiguity and to gain a better understanding of the hydrology of geothermal systems, which are embedded in a highly heterogeneous host medium.

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Section: Fracture Propertiesmentioning

confidence: 99%

Numerical modeling of fluid effects on seismic properties of fractured magmatic geothermal reservoirs

et al. 2017

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“…Strength, deformation, and permeability coupling of rock joints have been widely investigated during the previous decades, and a large amount of experimental works and models are available in the literature. Representative works include references [1][2][3][4][5][6][7][8][9][10][11][12][13], to cite a few. A more complete review may be found for instance in the book by Indraratna and Ranjith [14].…”

Section: Introductionmentioning

confidence: 99%

Micromechanics approach to poroelastic behavior of a jointed rock

Maghous

Dormieux

Kondo

et al. 2011

Num Anal Meth Geomechanics

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International audienceThe formulation of macroscopic poroelastic behavior of a jointed rock is investigated within the framework of a micro-macro approach. The joints are modeled as interfaces, and their behavior is modeled by means of generalized poroelastic state equations. Starting from Hill's lemma extended for a jointed medium and extending the concept of strain concentration to relate the joint displacement jump to macroscopic strain, the overall poroelastic constitutive equations for the jointed rock are formulated. The analysis emphasizes the main differences and similarities of the resulting behavior with respect to that characterizing ordinary porous media. It is shown that, unlike ordinary porous media, conditions on the poroelastic parameters of joints are required for the macroscopic drained stiffness to entirely define the poroelastic behavior. This is achieved, for instance, if the joint network is characterized by a unique Biot coefficient. Extension of the analysis to non-linear poroelasticity is also outlined. Finally, the theoretical formulation is applied to two particular cases of jointed rock for which explicit expressions of the overall poroelastic parameters are derived. © 2011 John Wiley and Sons, Ltd

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“…According to Barton and de Quadros (1997) experiments have shown that the roughness and aperture of a rock joint are the most important factors governing fluid flow through fractures. Li et al (2008) found that rough fractures exposed for shear displacement of 4-16 mm, experienced a significantly increase in both hydraulic and mechanic apertures compared with the same shear displacement in smoother fractures.…”

Section: Background Theorymentioning

confidence: 99%

Investigation and assessment of pre-grouted rock mass

Strømsvik

Gammelsæter²

2020

Bull Eng Geol Environ

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Pre-grouting is a technique for reducing water ingress into tunnels and caverns by grouting fractures and joints prior to excavation. This study investigates pre-grouted rock mass to evaluate grout penetration in fractures and transmissivity of water in the rock mass surrounding the built tunnel, with the use for core drilling, OTV, high-precision water injection tests and core logging. The study was performed in three tunnel localities, in tunnels excavated in connection with the Follo Line project in Norway, where pre-grouting was performed using cement-based grouts. It was found less cement than expected in fractures with small apertures, compared with results of grout penetrability in laboratory studies of similar grouts. Further, it was found that fractures in coarse-grained rock types had rougher fracture surfaces and higher hydraulic apertures, than fractures in fine-grained rock types. It was also found that fractures with smoother surfaces had smaller hydraulic apertures in general. Hydraulic jacking was evidenced during the pre-grouting in this area, which is likely to have contributed to unnecessary high grout consumption.

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Joint aperture and roughness in the prediction of flow and groutability of rock masses

Cited by 74 publications

References 5 publications

Numerical modeling of fluid effects on seismic properties of fractured magmatic geothermal reservoirs

Numerical modeling of fluid effects on seismic properties of fractured magmatic geothermal reservoirs

Micromechanics approach to poroelastic behavior of a jointed rock

Investigation and assessment of pre-grouted rock mass

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