Determination of permeability in anisotropic rock-masses from integral samples

Rocha, Manuel; Franciss, Fernando Olavo

doi:10.1007/bf01237875

Cited by 17 publications

(2 citation statements)

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“…It may be postulated that an increasing dilation will cause a proportional decrease in the interstitial pore fluid pressure, but this will depend on the rate of displacement or volumetric change in relation to the rate of percolation of the fluids; it depends on the conditions of drained or undrained media and the rate at which the drainage could take place. These conditions and the complexity of the problem are discussed by Lane (1969) (Snow, 1968a(Snow, , 1969Rocha and Franciss, 1977), where the emphasis has been on different conditions for the fractures (degree of opening, filling material, roughness of the surfaces, etc.) and on the determination of the permeability coefficient.…”

Section: = (5)mentioning

confidence: 98%

A correlation between the evolution of mineralizing fluids and the geomechanical development of a shear zone as illustrated by the Henderson 2 Mine, Quebec

Guha

Archambault²,

Leroy³

1983

Economic Geology

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The Henderson Cu-Au deposit is contained within the metaanorthosite of the Dore Lake Complex, located at the eastern end of the Chibougamau-Matagami greenstone belt. Two ore zones, one enclosed within a shear zone (zone B) and the other in a subsidiary structure (zone D) offer an ideal situation to study the correlation between the mechanical development of a shear zone and its subsidiary structure and the evolution of mineralizing fluids. A geomechanical interpretation demonstrates thatat the onset of the development of the shear zone, subsidiary fracture patterns are developed in second order faults in the following sequence. At peak strength Riedel shears (R and R') are formed which propagate out into the walls of the shear zones producing the zone D structure. After peak strength, restraint (P) shears are developed in the thrust attitude within the shear zone. Principal displacement shears (D) developed toward residual strength in the direction of movement. The continuation of the shear displacement gives rise to schistosities within the main shear zone. While the main shear zone and the P and D shears within the main shear zone were in continual movement, the subsidiary zone D structure, once formed retained a simple fracture pattern and moved little in comparison to the main shear zone. The above model makes necessary an examination of the mechanics of dilation which created openings for fluid movements and ore concentrations. The general principle involves the mechanics of the overriding of irregular planes and surfaces and the work performed by the normal pressure a during the dilation or contraction of the system. Application of the shear fracture dilatancy model explains the dilation mechanisms in zones B and D. Although the effect of interstitial fluid pressure is incompletely known, increasing dilation should bring about a reduction of the pore fluid pressure which will change the effective normal stress and aid fluid movement.Mineralizing fluids introduced into this shear environment show a similar pattern of evolution, with a wider range of homogenization and halite disappearance temperatures in the more active zone B than within zone D. Systematic variations of Ca/Na and Ca/Mg ratios in the fluid between zones B and D indicate migration and accompanying chemical changes of the fluid from zones B to D, in keeping with the evolution of the main shear zone and its subsidiary structure. These correlations suggest strongly that fluid inclusion studies can be useful for documenting geomechanical processes.

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Section: = (5)mentioning

confidence: 98%

A correlation between the evolution of mineralizing fluids and the geomechanical development of a shear zone as illustrated by the Henderson 2 Mine, Quebec

Guha

Archambault²,

Leroy³

1983

Economic Geology

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“…Nonetheless, a case in British Columbia, Canada, has shown that equivalent porous media model may return valid results and be useful for characterizing and quantifying hydraulic properties of fractured rock aquifers at a regional scale (Surrete 2006). Structural domains were defined by using joint density data and modeling with a stochastic, discrete joint system of equivalent porous media ( Fig (Bianchi & Snow 1968;Snow 1968Snow , 1969Snow , 1970Rocha & Franciss 1977;Long et al 1982;Oda 1985;Raven 1986). For illustration purposes, two of these studies of permeability tensors are further described.…”

Section: Equivalent Porous Media Models and The Permeability Tensormentioning

confidence: 99%

Structural hydrogeology in the Kenogami uplands, Quebec, Canada /

Silva¹

2012

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Characterizing the joint system is a very significant component of investigations on fractured rock aquifers, as the secondary porosity controls the groundwater flow. It is also important to analyze the types of interactions between the joints, e.g., the types of termination and the dominancy of a certain joint set, since such information helps to understand the tectonic events that were responsible for the generation of the joint systems in the aquifer. Moreover, the current stress field is usually the most significant in controlling joint aperture, which plays a major role in groundwater flow.The main objective of this work is to characterize an aquifer in fractured crystalline rocks with a fairly homogeneous lithology, defining a hydrogeological model of the study area, through structural surveys at different scales and hydrogeologic data analyses. This study was carried out in the Kenogami uplands, within the Saguenay graben, Quebec. It aimed to answer the following questions: (1) is there a structured joint system in the bedrock, that is, is it possible to identify preferential joint orientations and structural domains? (2) Can joint systems be defined at different scales, e.g. regional and local scales? If yes, are there any relationships between the systems observed at different scales? (3) Can any correlation between the joint system(s) and the past and present stress fields be identified? (4) Is there a relationship between the hydrogeological properties obtained from boreholes and the joint system(s)?The structural survey involved three main phases. First, a characterization at the regional scale of the joint system is derived from air photo interpretation, lineament analysis, and a general field survey at selected sites. The latter involves the investigation IV of the spatial distribution of the main joint sets, and the study of the relative ages of joint sets and past stress field components conducted on horizontal outcrops. Second, a detailed structural survey of selected road cuts was carried out to define and characterize the main joint sets that compose the joint system in the study area. Third, the realization of geophysical borehole logging provided valuable information at depth, especially regarding subhorizontal joint sets. These steps allowed to answer the questions proposed in the beginning of this research.This project allowed the characterization of an aquifer in fractured crystalline rocks, regarding the following aspects: joint systems at different scales, past stress fields, hydraulic properties and the possible relationships between these parameters. The methodology adopted may be applied to other studies on fractured rock aquifers.Finally, a conceptual model was developed for the fractured rock aquifer in the Kenogami uplands, using the unit block approach. This model may be extrapolated to a regional scale, and it reflects the predominance of the subvertical joints in the study area.Other contributions from this work include the introduction of procedures for applying Terzag...

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