HR: 1330h
AN: H42F-1145    [PDF]
TI: Part II - Evaluation Of Coupled Hydromechanical Analysis Of A Fractured Rock Mass By The Multi-scale Comparison Between Experimental And Numerical Modeling Datas From The Coaraze Natural Site.
AU: * Frederic, C
EM: cappa@geoazur.unice.fr
AF: Geosciences Azur CNRS-UNSA, 250, rue A. Einstein - Les Lucioles I - Sophia Antipolis, Valbonne, AM 06560 France
AU: Yves, G
EM: guglielmi@geoazur.unice.fr
AF: Geosciences Azur CNRS-UNSA, 250, rue A. Einstein - Les Lucioles I - Sophia Antipolis, Valbonne, AM 06560 France
AU: Veronique, M
EM: Veronique.Merrien@mines.inpl-nancy.fr
AF: LAEGO, Ecole des Mines - Parc de Saurupt, Nancy, 54042 France
AU: Imad, K
EM: Kadiri@mines.inpl-nancy.fr
AF: LAEGO, Ecole des Mines - Parc de Saurupt, Nancy, 54042 France
AB: A comparison between 2D UDEC numerical modeling and in-situ hydromechanical (HM) measurements is performed to better understand the coupling processes in a fractured media. Measurements come from the Coaraze site that is a natural 19000~m$^3$ site where geometrical, hydraulical and mechanical parameters are known. Pressure and normal displacements on 10 single fractures inside the site and surface tilting are permanently measured. Repetitive hydraulic loadings are produced by the closure of a floodgate located on a spring of the site. A 100~kPa water pressure increase cause instantaneous elastic deformation of fractures and rock matrix. Those datas were used to evaluate a coupled hydromechanical numerical analysis at the single fracture and at the whole rock mass scales. At the single fracture scale, the high non-linear relationship between measured normal displacements and pressures is well explained with a variable normal joint stiffness model modified from Bandis law in order to take into account the joint environment. The more general deformation of the rock mass results from the complex heterogeneous stress-permeability behavior of the fracture network. High permeable fractures apertures change of a factor 2 in response to changing fluid pressure whereas there is a low change of low permeable fractures apertures. A 2D UDEC model of the entire rock mass that takes into account the heterogeneity of constant normal joints stiffnesses deduced from single fracture analysis and permeabilities measured in the field best fit experimental datas. Nevertheless, model results remain far from measurements (10 to 20% differences) mainly because fractures network geometry and permeabilities high heterogeneity need to be simplified to run the model. This analysis shows that it is possible to deduce hydromechanical non-linear laws from in-situ hydromechanical tests on single fractures with a good accuracy. Nevertheless, even with these laws taken as input parameters, it remains insufficient to restore a satisfying general behavior of a rock mass.
DE: 1829 Groundwater hydrology
SC: Hydrology [H]
MN: 2003 Fall Meeting