Utilisation d'un modèle stochastique de réseaux de fractures pour étudier les propriétés hydrauliques d'un massif fissuré

1989 ◽  
Vol 26 (2) ◽  
pp. 313-323
Author(s):  
Lahcen Ait-Ssi ◽  
Jean-Pierre Villeneuve ◽  
Alain Rouleau
Keyword(s):  
Rock Mass ◽  
Hydraulic Properties ◽  
Model Simulation ◽  
Water Injection ◽  
Stochastic Simulations ◽  
Fracture Aperture ◽  
Modèle Stochastique ◽  
Fracture System ◽  
Fracture Porosity ◽  
Fractured Medium

This study of the hydraulic properties of a fractured rock mass is based on data from field injection tests and fracture measurements, and on simulations of the fracture system in the bedrock upstream from the Daniel Johnson dam at Manic 5. Analysis of water injection tests indicates that the bedrock can be divided into two zones with respect to the permeability. The more permeable zone, which is the object of this study, shows a log-normal distribution of the hydraulic conductivities.Using several stochastic simulations of fracture networks, the fracture aperture has been adjusted gradually to reproduce the rock mass permeability estimated from injection tests. The results show that the fracture system geometry, as well as the fracture porosity and the fracture lengths and densities, influences widely the hydraulic properties of a fractured medium and particularly the fracture porosity. Also, the estimation of the fracture porosity is sensitive to a number of other factors, including the assumed hydraulic boundary conditions, the field estimation of the hydraulic conductivities, and the orientation of the simulation planes. Key words: fissured media, fracture porosity, stochastic model, simulation, sensitivity analysis, dam.

Investigations of Hydraulic Properties in Crystalline Rock.

1983 ◽  
Vol 26 ◽  
Author(s):  
Leif Carlssn ◽  
Anders Winberg ◽  
Björn Rosander
Keyword(s):  
Rock Mass ◽  
Hydraulic Conductivity ◽  
Hydraulic Properties ◽  
Water Injection ◽  
Three Dimensional ◽  
Crystalline Rock ◽  
Fracture Frequency ◽  
Effective Hydraulic Conductivity ◽  
Constant Head ◽  
Total Fracture

ABSTRACTHydraulic properties of crystalline rock from four potential repository sites in Sweden were analysed. The hydraulic conductivity of the bedrock was established by means of transient water-injection tests with constant head conducted in 25 m sections. The bedrock at the sites was divided into different hydraulic units. An effective hydraulic conductivity was calculated for the rock mass at each site. This was done on the basis of the frequency distribution of all measured values within this unit. A log-nornal distribution was found to fit the data reasonably well. Regression analysis of hydraulic conductivity as a function of depth indicated similar relationships between the four sites. At a depth of 500 m the effective hydraulic conductivity for three-dimensional flow was about 5.10-11 m/s.The fracture frequency of the sites was established from existing core-logs. At depths of about 500 m the mean fracture frequency of the rock mass at the four sites was 1.8-2.5 fractures per meter. Of this total fracture frequency only a a certain proportion is considered to be hydraulically conductive. This proportion was established from results of hydraulic tests perforned in 2 or 3 m sections. Results obtained indicated a frequency of hydraulically conductive fractures of 0.1-0.3 fractures per meter in the rock mass at depths below 300 m.

Change in Hydraulic Properties of Rock Mass Due to Tunnelling

2014 ◽  
pp. 937-940
Author(s):  
Bernard Millen ◽  
Giorgio Höfer-Öllinger ◽  
Johann Brandl
Keyword(s):  
Rock Mass ◽  
Hydraulic Properties

Hydromechanical response of a bedded argillaceous rock formation to excavation and water injection

2015 ◽  
Vol 52 (1) ◽  
pp. 1-17 ◽  
Author(s):  
A.D. Le ◽  
T.S. Nguyen
Keyword(s):  
Rock Mass ◽  
Pore Pressure ◽  
Damage Zone ◽  
Water Injection ◽  
Constitutive Relationship ◽  
Opalinus Clay ◽  
Anisotropic Plastic ◽  
Mont Terri ◽  
Excavation Damage

Opalinus clay is a candidate host formation for the geological disposal of nuclear wastes in Switzerland. The understanding of its long-term mechanical (M) and hydraulic (H) behaviour is an essential requirement for the assessment of its performance as a barrier against radionuclide transport. To study the HM response of Opalinus clay, a microtunnel, 13 m in length and 1 m in diameter, was excavated in that formation at the Mont Terri Underground Research Facility. The rock mass was equipped with sensors to measure the deformation and pore pressure in the rock mass during and after the excavation. A mathematical model that couples the equations of flow and mechanical equilibrium was developed to simulate the HM response of the rock mass. An anisotropic plastic constitutive relationship, based on a microstructure tensor approach, was incorporated in the model. Creep was also considered, as well as the anisotropy of permeability. It is shown that the model satisfactorily predicts the shape and extent of the excavation damage zone (EDZ), deformation, and pore pressure in the rock mass. It is also shown that anisotropy and creep play an important role in the HM response of the rock mass to excavation. The model was further used to simulate water injection tests performed at the test section in the microtunnel. The results show that EDZ, due to its high permeability, is a preferential groundwater flow path along the microtunnel.

ON TWO-PHASE FLOW IN FRACTURED MEDIA

2002 ◽  
Vol 12 (08) ◽  
pp. 1075-1107 ◽  
Author(s):  
LI-MING YEH
Keyword(s):  
Two Phase Flow ◽  
Fractured Media ◽  
Phase Flow ◽  
Fracture System ◽  
Two Phase ◽  
Fractured Medium ◽  
Matrix Block ◽  
Matrix Blocks ◽  
Capillary Pressures

A model describing two-phase, incompressible, immiscible flow in fractured media is discussed. A fractured medium is regarded as a porous medium consisting of two superimposed continua, a continuous fracture system and a discontinuous system of medium-sized matrix blocks. Transport of fluids through the medium is primarily within the fracture system. No flow is allowed between blocks, and only matrix-fracture flow is possible. Matrix block system plays the role of a global source distributed over the entire medium. Two-phase flow in a fractured medium is strongly related to phase mobilities and capillary pressures. In this work, four relations for these functions are presented, and the existence of weak solutions under each relation will also be shown.

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