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To meet the special requirements for sealing the Lotschberg and St Gotthard base tunnels in Switzerland, a novel testing system was needed for evaluation of different methods. Requirements to be tested included water-tightness, draining effect, pressure transfer and stability behaviour. The testing system included a number of sectors: material tests to check stability, sustained pressure tests, pressure-shearing tests and tests under site conditions. The system applied turned out to be fully feasible and practice-related. At the end of the first cycle of testing seven sealing systems that complied with all requirements were accepted for the register of approved systems, while more have since been added., To meet the special requirements for sealing the Lotschberg and St Gotthard base tunnels in Switzerland, a novel testing system was needed for evaluation of different methods. Requirements to be tested included water-tightness, draining effect, pressure transfer and stability behaviour. The testing system included a number of sectors: material tests to check stability, sustained pressure tests, pressure-shearing tests and tests under site conditions. The system applied turned out to be fully feasible and practice-related. At the end of the first cycle of testing seven sealing systems that complied with all requirements were accepted for the register of approved systems, while more have since been added.