Poroplastic modelling of the excavation and ventilation of a deep cavity

Abstract

SUMMARYA plastic deviatoric model with hardening is developed on the basis of geomechanical tests performed in the saturated case on low permeable porous material such as argillite. This model is a generalized MohrCoulomb plastic criterion combined with a Drucker-Prager plastic potential and the hardening parameter is the plastic distortion. Three different hardening functions have been introduced on the basis of triaxial tests: an increase of friction angle, a decrease of cohesion after a threshold and a contractancy to dilatancy transition for volumetric plastic strain. This plastic model has been adapted to the partially saturated case. The effective stress is expressed thanks to the equivalent interstitial pressure p: Numerical results are presented for the excavation and monotonous ventilation of a deep cylindrical cavity. A first plastification due to excavation is followed by a second one due to desaturation. The extent of the non-saturated zone provokes an extent of a plastic zone in the rock mass. Analysis shows that the origin of the plastification can be found in the deviatoric stresses because mean effective stresses are compressive during drying.

Study of the soil–atmosphere moisture exchanges through convective drying tests in non‐isothermal conditions

“…Vapour exchanges take place from the materials surface to the surrounding air. In many cases, vapour transfers are modelled by a decrease in the water pressure at the boundary down to the corresponding surrounding suction [8,16]. This boundary condition relies on the assumption of a quasi-instantaneous equilibrium between the air relative humidity of the atmosphere and the one of the porous medium.…”

“…The temperature and the relative humidity of the atmosphere are imposed at the corresponding node. Heat and flow transfers with the exterior are described by Equations (2) and (16). Mass and heat transfer coefficients computed from the drying experiments in Section 3 are used in the boundary condition expressions.…”

“…The proposed formulation, based on the existence of a boundary layer, allows a good reproduction of the kinetic of the materials desaturation quantified during the drying experiments. Indeed, such a formulation avoids the overestimation of the vapour exchanges obtained when the desaturation of the soil is achieved imposing numerically the capillary pressure at the soil boundary to the ambient suction [8,16]. Finally, numerical modellings of the drying tests in non-isothermal conditions are performed (Section 5), followed by the analysis of the moisture transport mechanisms in the materials (Section 6).…”

Study on the Elastoplastic Damage-Healing Coupled Constitutive Model of Mudstone

“…At present, the worldwide recognized nuclear waste disposal method is to bury nuclear waste deep underground for storage [1][2][3][4]. Among the many geologic bodies, mudstone is being paid extensive attention due to its characteristics of low permeability and good rheological and self-healing performance, which has been the main parent rock for nuclear waste disposal.…”

On boundary condition in tunnels under partial saturation

“…On the other hand, the relative humidity in the gallery is usually controlled through an ''air conditioning system''. This could be modelled by a decrease of the pore pressure down to the corresponding suction at the end of the excavation [Hoxha et al, 2004]. This boundary condition relies on the assumption of a quasi-instantaneous equilibrium between the gallery relative humidity and the wall pore pressure.…”