The Swiss program for the deep-geological disposal of radioactive waste: Status of site selection and concept demonstration

Peer Reviewe

Numerical Implementation of a Critical State Model for Soft Rocks

This paper details the basic tasks for the numerical implementation of a simple elasto-plastic critical state model for bonded materials (i.e. soft rocks-hard soils) into the finite element program SNAC developed at the University of Newcastle in Australia. The first task described focusses on the derivation of the incremental constitutive relationships used to represent the mechanical response of a bonded/cemented material under saturated conditions. The second task presents how these stress-strain relations can be numerically integrated using an explicit substepping scheme with automatic error control. The third task concentrates on the verification of the substepping algorithm proposed. The model used to represent the saturated mechanical response of a bonded material combines the modified Cam clay with the constitutive relationships for cemented materials proposed in Gens & Nova (1993), but incorporates some flexibility on the degradation law adopted. The role of suction and other relevant aspects of unsaturated behaviour are also discussed at the end of the paper

Experimental Design for in situ Characterization of the Callovo-Oxfordian Pore Water Composition at 85°C

AbstractWhen emplaced into deep geological disposal cells, the high-level radioactive waste packages will induce a transitory temperature increase in the surrounding geological environment. High temperatures will have an influence on the composition of water that will flow into the cells and come in contact with the disposal materials. An in situ experiment which aims at characterizing the Callovo- Oxfordian pore water at 85°C has been running since 2012. This paper presents the design of the experiment and the predictive thermo-hydro-mechanical (THM) modeling results

Modelling a heater experiment for radioactive waste disposal

International audienceThis paper presents the Canadian Nuclear Safety Commission's modelling of coupled thermal, hydraulic and mechanical (THM) processes and their influence on the performance of the engineered barrier system (EBS) and the host rock. The coupled THM processes were monitored during a heater experiment called HE-E, performed in an Opalinus Clay formation at the Mont Terri Rock Laboratory in Switzerland. The HE-E experimental set-up consisted of two EBS sections emplaced in an existing tunnel of the Underground Rock Laboratory. This paper focuses on the model development, parametric analysis, model calibration and verification with the field test data. The influence of THM processes on the EBS and host rock performance and the implications on the design and safety assessment of geological disposal repository systems are discussed. © 2019 Published with permission by the ICE under the CC-BY 4.0 license

Analysis of hydro-mechanical processes in a ventilated tunnel in an argillaceous rock on the basis of different modelling approaches

International audienceIn this paper, a modelling benchmark exercise from the DECOVALEX-2011 project is presented. The benchmark is based on the performance and results of a laboratory drying test and of the ventilation experiment (VE) carried out in the Mont Terri Underground Rock Laboratory (URL). Both tests involve Opalinus clay. The work aims at the identification, understanding and quantification of mechanisms taking place during the ventilation of a gallery in argillaceous host rocks on one hand and at investigating the capacity of different codes and individuals to reproduce these processes on the other hand. The 4-year in situ VE took place in a 1.3 m diameter unlined tunnel and included two resaturation–desaturation cycles. The test area was equipped with over one hundred sensors (including the global water mass balance of the system, relative humidity (RH), water content, liquid pressure, relative displacement and concentration of some chemical species) to monitor the rock behaviour during ventilation. The laboratory drying experiment, carried out before the VE, was designed to mimic the in situ conditions. The work was organized in a progressive manner in terms of complexity of the computations to be performed, geared towards the full hydro-mechano-chemical (HMC) understanding of the VE, the final objective. The main results from the modelling work reported herein are that the response of the host rock to ventilation in argillaceous rocks is mainly governed by hydraulic processes (advective Darcy flow and non-advective vapour diffusion) and that the hydro-mechanical (TM) back coupling is weak. A ventilation experiment may thus be regarded as a large scale-long time pump test and it is used to determine the hydraulic conductivity of the rock mass