Evolution spatio-temporelle des zones endommagées (EDZ) : Retour d'expérience du site argileux de Tournemire (France)

Titre du congrès :ISRM 2007 11h International Congress on Rock Mechanics Ville du congrès :Lisbonne Date du congrès :09/07/2007

The Tournemire experimental site enables the assessment of the EDZ (Excavation Damaged Zone) around a century old tunnel, an eleven year-old gallery and a four year-old gallery. The three openings have an EDZ of the same extent, i.e approximately 20 % of the mean radius of the excavation. However, the typology of the EDZ fracturing seems to be affected by the age of the opening. The EDZ fracturing around the old tunnel resembles onion skins whereas the new galleries have an EDZ fracturing parallel to the bedding planes. An EDZ explanation has been derived by considering a time-dependent failure mechanism governed by a desaturation/resaturation processes. At first, these processes induced probably a tensile failure around the new galleries. Later, these processes cause a gradual weakening of the rock which can result in a compressive failure around the old tunnel. The time-dependent failure mechanism is partly confirmed by hydromechanical simulations carried out under unsaturated conditions.