1. Introduction

A model of discontinuity in a saturated porous medium with hydro-mechanical coupling is presented here, which accounts for the following coupled phenomena:

• the preferential flow of intersticial fluid into the joint, which depends on the opening of the crack,

• fluid exchanges between the joint and the porous medium,

• the deformation of the massif and the crack opening under the action of crack pressure,

• the propagation of the crack.

Depending on the law of behavior chosen, this model makes it possible to model the propagation of the crack or simply the behavior of a hydraulic joint that is already completely open. This joint element is based on the formulation of the joint elements already present in Code_Aster in classical mechanics. Degrees of hydraulic freedom are added in order to take into account the flow in the crack and the exchanges of fluid with the porous mass.

Propagation is represented by a cohesive zone model and the regularized cohesive laws of mechanical joint elements are used. In order to model the behavior of fully open hydraulic joints, the Bandis law of behavior is introduced.

The crack path is discretized by these joint elements while the rest of the structure is meshed by solid THM elements already existing in Code_Aster.

Here we describe the hydraulic and mechanical conservation equations along the discontinuity, the corresponding laws of behavior, as well as the numerical integration of these equations.

This work is part of the GNR MoMAS (program TB5, Excavation Damage Zone).