Water flow in a natural rock fracture as a function of stress and sample size

Raven, K.G.; Gale, J.E.

doi:10.1016/0148-9062(85)92952-3

Cited by 319 publications

(154 citation statements)

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“…The hydromechanical behavior of fractured rock has been extensively studied through laboratory experiments on single fractures [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], field testing [5,[19][20][21][22][23][24][25][26][27][28][29][30][31], and numerical simulations [32][33][34][35][36][37][38][39][40][41][42]. Most of the field studies have been conducted at great depth in fractured hard rock, in which the permeability of the rock matrix is generally low and fractures act as dominating fluid conducting pathways.…”

Section: Introductionmentioning

confidence: 99%

Hydromechanical modelling of pulse tests that measure fluid pressure and fracture normal displacement at the Coaraze Laboratory site, France

Cappa

Guglielmi

Rutqvist

et al. 2006

International Journal of Rock Mechanics and Mining Sciences

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In situ fracture mechanical deformation and fluid flow interactions are investigated through a series of hydraulic pulse injection tests, using specialized borehole equipment that can simultaneously measure fluid pressure and fracture displacements. The tests were conducted in two horizontal boreholes spaced one meter apart vertically and intersecting a near-vertical highly permeable fault located within a shallow fractured carbonate rock. The field data were evaluated by conducting a series of coupled hydromechanical numerical analyses, using both distinct-element and finite-element modeling techniques and both two-and three-dimensional model representations that can incorporate various complexities in fracture network geometry.One unique feature of these pulse injection experiments is that the entire test cycle, both the initial pressure increase and subsequent pressure fall-off, is carefully monitored and used for the evaluation of the in situ hydromechanical behavior. Field test data are evaluated by plotting fracture normal displacement as a function of fluid pressure, measured at the same borehole. The resulting normal displacement-versus-pressure curves show a characteristic loop, in which the paths for loading (pressure increase) and unloading (pressure decrease) are different. By matching this characteristic loop behavior, the fracture normal stiffness and an equivalent stiffness (Young's modulus) of the surrounding rock mass can be back-calculated.Evaluation of the field tests by coupled numerical hydromechanical modeling shows that initial fracture hydraulic aperture and normal stiffness vary by a factor of 2 to 3 for the two 2 monitoring points within the same fracture plane. Moreover, the analyses show that hydraulic aperture and the normal stiffness of the pulse-tested fracture, the stiffness of surrounding rock matrix, and the properties and geometry of the surrounding fracture network significantly affect coupled hydromechanical responses during the pulse injection test. More specifically, the pressure-increase path of the normal displacement-versus-pressure curve is highly dependent on the hydromechanical parameters of the tested fracture and the stiffness of the matrix near the injection point, whereas the pressure-decrease path is highly influenced by mechanical processes within a larger portion of the surrounding fractured rock.

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Section: Introductionmentioning

confidence: 99%

Hydromechanical modelling of pulse tests that measure fluid pressure and fracture normal displacement at the Coaraze Laboratory site, France

Cappa

Guglielmi

Rutqvist

et al. 2006

International Journal of Rock Mechanics and Mining Sciences

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“…Selon la loi cubique, l'écoulement dans cette fracture est proportionnel au cube de son ouverture. Pourtant, les travaux expérimentaux sur l'écoulement d'un fluide dans une fracture naturelle ou induite ont montré que l'écoulement ne respecte pas toujours cette loi (figure 2.1) (Iwai, 1976;Gale, 1982;et Raven et Gale, 1985). On a attribué ces déviations de la loi cubique à la rugosité de la surface de la fracture et à la tortuosité de l'écoulement.…”

Section: Processus Hydromécaniquesunclassified

“…Par exemple, les travaux de Iwai (1976), Tsang et Witherspoon (1981), Raven et Gale (1985), Barton et al (1985), Gentier (1986) et Cook (1992, ont souligné que l'augmentation de la contrainte normale sur une fracture provoque une diminution rapide de sa transmissivité. À des niveaux élevés de contrainte normale, cependant, la transmissivité de la fracture tend à devenir constante.…”

Section: Processus Hydromécaniquesunclassified

Étude des processus chimio-hydro-mécaniques dans un massif rocheux fracturé perturbé par une exploitation minière :

Benlahcen¹

2003

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This study on the chemical, hydraulic and mechanical processes and their coupling, was conducted at the Bouchard-Hébert Mine, located in the Abitibi Mining District in Québec, Canada. In this mine environment, the acidic water migrating from the old mine workings to the new ones, in combination with the perturbed geomechanical stress field caused by the excavations, affect the rock mass permeability. Both field work and laboratory experiments were conducted in order to investigate these processes, particularly in the rock mass portion located between the two mine workings (drift at level 6A).Results of discontinuity mapping show that at the western part of the drift at level 6A (from 10600E to 10900E), the rock mass contains two sets of fractures: one set is subhorizontal (dip between 0° and 30°) with a trace length between 1 and 1.5 m, and the other set is subvertical (dip between 75° and 90°). This subvertical set is divided into two groups depending on their trace length: one group includes fractures with a trace length between 0.5 and 2 m, and the second group comprises fractures with a trace length between 3 and 3.5 m. The fracture density of these two sets of fractures varies from 1 to 6 m" 1 and their veins are 2 mm in width. At the eastern part of the drift at level 6A (from 10900E to 11200E), the rock mass contains the same two sets of fractures observed at the western part, plus a set of fractures with a moderate dip (between 15° and 45°) with NE trend. This later set of fractures is less frequent and has a variable trace length between 0.5 and 2.5 m; their veins have a width of 2 mm. The fracture density of all the fracture set is between 1 and 4 m' 1 . Although the rock mass at the eastern part of the drift at the level 6A contains three sets of fractures, it is less permeable than the one located at the western part considering its lower fracture density. Consequently, grounwater flow would be more intense in the rock mass at the western part of the drift at the level 6 A of the mine.The results of hydraulic testing in boreholes in the rock mass located immediately under the drift 6A and over a lengh of 48 m, have shown that in the eastern part of this excavation, the hydraulic conductivity of the rock mass is low and constant, between 1 xlO" 10 and 1 xlO " n ms"1 . In the central part of this drift, located just under the old excavations, the rock mass hydraulic conductivity is higher and increases with depth from 1 xlO" 11 and 1 xlO ' 6 ms" 1 , which is in accordance with the higher fracture density in this part of the drift.Hydrogeochemical results show that waters sampled from boreholes at the mine are of neutral pH and contain high concentrations in ions, such as Ca, SO4 and metals. Calcium originates from the dissolution of calcite which is in abundance in fractures. Sulfate and metals originate from sulfide mineral oxidation present in fractures as well as in the rock matrix. Waters at a bulkhead at the base of the old excavations and the mixing waters at the surface, pumped from all ...

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“…A number of studies on fluid flow and solute transport in a single fracture has been conducted so far and include laboratory or field experiments [1][2][3][4][5][6][7][8] and numerical experiments [9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of Spatial Behavior of Solute Particle Transport in Single Fracture with Variable Apertures

Jeong

2018

Water

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Abstract:The aim of this study is to numerically analyze spatial behaviors of solute particle transport in a single fracture with spatially correlated variable apertures under application of effective normal stress conditions. The numerical results show that solute particle transport in a single fracture is strongly affected by spatial correlation length of variable apertures and applied effective normal stress. As spatial correlation length increases, mean residence time of solute particles decreases and tortuosity and Peclet number (a dimensionless number representing the relationship between the rate of advection of solute particles by the flow and the rate of diffusion of solute particles) also decreases. These results indicate that the geometry of the aperture distribution is favorable to solute particle transport when the spatial correlation length is increased. However, as effective normal stress increases, the mean residence time and tortuosity tend to increase but the Peclet number decreases. The main reason for a decreasing Peclet number is that the solute particle is transported by one or two channels with relatively higher localized flow rates owing to increase in contact areas resulting from increasing effective normal stress. Based on the numerical results of the solute particle transport produced in this study, an exponential-type correlation formula between the mean residence time and the effective normal stress is proposed.

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Water flow in a natural rock fracture as a function of stress and sample size

Cited by 319 publications

References 13 publications

Hydromechanical modelling of pulse tests that measure fluid pressure and fracture normal displacement at the Coaraze Laboratory site, France

Hydromechanical modelling of pulse tests that measure fluid pressure and fracture normal displacement at the Coaraze Laboratory site, France

Étude des processus chimio-hydro-mécaniques dans un massif rocheux fracturé perturbé par une exploitation minière :

Numerical Study of Spatial Behavior of Solute Particle Transport in Single Fracture with Variable Apertures

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