Hydro-mechanical behavior of fractures: 2D, F.E.M. modeling

in Auriault, J. L.; Geindreau, C.; Royer, P. (Eds.) Poromechanics II (2002)

A numerical approach for modeling the coupled hydro-mechanical fracture behavior is proposed. The movement of fluids through rock fractures and consequently the evolution of their hydraulic conductivity ... [more ▼]

A numerical approach for modeling the coupled hydro-mechanical fracture behavior is proposed. The movement of fluids through rock fractures and consequently the evolution of their hydraulic conductivity is an important subject in many petroleum related activities, mainly concerning the change of well productivity during the reservoir life. It is well known that the flow in the fractures is strongly controlled by the fracture apertures. Recent investigations on the distribution of the apertures in natural fractures suggest that the cubic law can, better than the Darcy law, predict the fluid flux through rough walled fractures as long as the appropriate average fracture aperture is used. A finite element code is developed to predict the influence that the stresses variation in the fracture has on the distributed hydraulic conductivity field. The proposed model combines the stochastic cubic law with a non-linear deformation function (hyperbolic) that is suggested to describe the stress-closure/opening curves of the joints and that allows to couple together the hydraulic and the mechanic fracture behavior. The relationships used and the validity of the present model are tested by means of the comparison between experimental data and numerical predictions (Bart 2000) in various bound-ary and loading conditions. Comparisons between the proposed new model and a no coupled one have also been performed. They show that the proposed coupled model allows for a more realistic description of the fracture behavior. [less ▲]

A pluridisciplinary model to predict municipal landfill life

Conference (2001)

Most degradation processes that occur within municipal wastes landfills result from different microbial activities interacting all along the landfill lifetime and that are influenced by several non ... [more ▼]

Most degradation processes that occur within municipal wastes landfills result from different microbial activities interacting all along the landfill lifetime and that are influenced by several non-biological factors. These complex biological and chemical processes require a multidisciplinary pattern in order to assess and control their environmental impact. Thanks to Walloon Region support, we have developed a pattern or model combining the evolution of different key parameters. Such parameters qualify biogas (composition, production rate), leachate (pH, BOD5, COD, volatile fatty acids, redox potential, nitrogen balance, humic acids...), or solid waste (moisture, settlement, cellulose content...). This paper presents relationships, including our model, between these parameters. Variations of pH, BOD5/COD ratio, sulfate concentration in leachates, gas composition analysis and settlement measures allow to predict landfill age, on a standard scale, since completion. Evaluation of cellulose and water content in refuse as well as settlement degree are useful to estimate the time required for complete biological degradation. [less ▲]

Numerical modelling of coupled transient phenomena

in Revue Française de Génie Civil (2001), 5(6), 719-743

The basic phenomena involved in thermo-hydro-mechanical processes in geomaterials have been described in the 1st chapter. The equations describing these phenomena are non-linear differential equations ... [more ▼]

The basic phenomena involved in thermo-hydro-mechanical processes in geomaterials have been described in the 1st chapter. The equations describing these phenomena are non-linear differential equations. Their solution can generally only be approximated thanks to numerical methods. This is the main subject of the present chapter. First the type of problems and the set of equations to be solved will be shortly recalled. Emphasis will be given on the non-linear contributions. In a second section, the mostly developed numerical method, i.e. the finite difference and the finite element methods will be discussed under the light of the problems to be treated. The iterative techniques allowing the solution of non linear equations will be described. A third section will be dedicated to the coupling terms and to their modelling. The question that rises then is How to model efficiently problems, which may differ highly from, the point of view of the time and length scales? [less ▲]

Clay barriers assesment : a coupled mechanical and moisture transfert model

(1999)

A thermo-hydro-mechanical model is presented to tackle the complex coupling problems encountered in clay barriers. A detailed formulation coupling the heat, moisture (liquid water and water vapour) and ... [more ▼]

A thermo-hydro-mechanical model is presented to tackle the complex coupling problems encountered in clay barriers. A detailed formulation coupling the heat, moisture (liquid water and water vapour) and, air transfer in a deformable unsaturated soil is given. The formulation of the Alonso-Gens’s mechanical model for unsaturated soil is also incorporated. The sensitivity to some parameters and their determinations are analysed. Finally, a small scale wetting – heating test on compacted bentonite is performed for validation; the numerical results are compared to the experimental measurements. [less ▲]

Comparisons of anisotropic elastoplastic laws applied to steel sheet

in International Conference NUMIFORM 1998 (1998, June)

Thermo-hydro-mechanical coupling in clay barriers

in Evangelista, Aldo; Picarelli, Luciano (Eds.) The Geotechnics of Hard soils, Soft Rocks (1998)

A complete thermo-hydro-mechanical model is presented to tackle the complex coupling problems encountered in clay barriers. A detailed formulation coupling the heat, moisture (liquid water and water ... [more ▼]

A complete thermo-hydro-mechanical model is presented to tackle the complex coupling problems encountered in clay barriers. A detailed formulation coupling the heat, moisture (liquid water and water vapour) and, air transfer in a deformable unsaturated soil is given. The formulation of the Alonso-Gens’s mechanical model for unsaturated soil is also incorporated. The sensitivity to some parameters and their determinations are analysed. Finally, a small scale wetting – heating test on compacted bentonite is performed for validation; the numerical results are compared to the experimental measurements. [less ▲]

Water movement effect on the strain localisation during a biaxial compression

in Proc. of NUMOG VI (1997, July)

Modellnig of the Hydromechanical Coupling for Non Linear Problems: Fully Coupled and Staggered Approaches

in Proc. of the 8th Int. Conf. of the Int. Ass. for Computer Methods and Advances in Geomechanics (1994, May)

3D Finite Element Modeling of Miscible Pollutant Transport by Groundwater in Saturated Zones.

in Congrès National Belge de Mécanique Théorique et Appliquée (1994)

A finite element code for subsidence problems: LAGAMINE

in Bulletin of Engineering Geology & the Environment (1993), 47(1 / avril), 5-11