Current challenges for scaling of tunnel drainage systems – Modelling approaches, monitoring tools and prevention strategies

Scaling of tunnel drainage systems comprises complex reaction mechanisms, which are essentially caused by the interaction of water with cement-based materials and the atmosphere. The resulting precipitation of CaCO3 in the drainage is an economically highly challenging task for tunnel operators with respect to maintenance and cleaning action. Hydrochemical modelling is used to decipher reaction mechanisms and thus to provide quantifications, which are required to develop monitoring tools, like in-situ alert systems, and prevention strategies, like application of low-eluting shotcrete and inhibitors.