Effect of squeezing on construction and structural safety of the Swiss high-level radioactive waste repository drifts  

作　　者：Alexandros N.Nordas Matteo Natale Linard Cantieni Georgios Anagnostou 

机构地区：[1]Department of Civil,Environmental and Geomatic Engineering,ETH Zurich,Zurich,8093,Switzerland [2]Department of Construction and Environment,National Cooperative for the Disposal of Radioactive Waste(Nagra),Wettingen,5430,Switzerland

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2024年第12期5162-5178,共17页岩石力学与岩土工程学报（英文）

摘　　要：The deep geological repository for radioactive waste in Switzerland will be embedded in an approximately 100 m thick layer of Opalinus Clay.The emplacement drifts for high-level waste(approximately 3.5 m diameter)are planned to be excavated with a shielded tunnel boring machine(TBM)and supported by a segmental lining.At the repository depth of 900 m in the designated siting region Nordlich Lagern,squeezing conditions may be encountered due to the rock strength and the high hydrostatic pressure(90 bar).This paper presents a detailed assessment of the shield jamming and lining overstressing hazards,considering a stiff lining(resistance principle)and a deformable lining(yielding principle),and proposes conceptual design solutions.The assessment is based on three-dimensional transient hydromechanical simulations,which additionally consider the effects of ground anisotropy and the desaturation that may occur under negative pore pressures generated during the drift excavation.By addressing these design issues,the paper takes the opportunity to analyse some more fundamental aspects related to the influences of anisotropy and desaturation on the development of rock convergences and pressures over time,and their markedly different effects on the two lining systems.The results demonstrate that,regardless of these effects,shield jamming can be avoided with a moderate TBM overcut,however overstressing of a stiff lining may be critical depending on whether the ground desaturates.This uncertainty is eliminated using a deformable system with reasonable dimensions of yielding elements,which can also accommodate thermal strains generated due to the high temperature of the disposal canisters.

关 键 词：Radioactive waste disposal SQUEEZING Opalinus clay ANISOTROPY Ground desaturation Transient consolidation Tunnel boring machine 

分 类 号：TU45[建筑科学—岩土工程]