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Hydro-mechanical analysis of SEALEX in-situ tests — Impact of technological gaps on long term performance of repository seals

Mokni, Nadia, Barnichon, Jean-Dominique
Engineering geology 2016 v.205 pp. 81-92
bentonite, engineering, homogenization, models, monitoring, sand, seals, uncertainty
The paper describes the observations and numerical analysis of the first SEALEX performance test PT-N1 installed in Tournemire Underground Research Laboratory (URL). The aim of this large-scale in-situ test is to investigate the impact of technological gaps on the long term performance of bentonite based seals. The swelling core consists of pre-compacted blocks of MX80 bentonite/sand mixture (70/30 in dry mass). An annular technological gap with variable width exists between the bentonite-based core and the host rock. The test is extensively instrumented for monitoring the main Hydro-Mechanical (HM) variables. Material parameters are determined from an extensive laboratory program carried out in the context of SEALEX project. To ensure an adequate interpretation of the test, the annular technological gap has been appropriately represented. A coupled HM formulation that incorporates the relevant processes involved in the problem under consideration has been adopted to analyse the evolution of the test. The paper presents and discusses the hydraulic and mechanical observations in the bentonite based core. Special attention is paid to the effect of technological gap on bentonite homogenisation as hydration progresses. The model was able to predict correctly the global HM behaviour of the bentonite based core considering the uncertainties and heterogeneities associated to the fabrication and installation processes of the bentonite based blocks. Technological gap was demonstrated to have an impact on dry density distribution.