Base tunnel comprises twin 2.5 km tubes, of which 1.8 km driven by traditional sprayed concrete techniques in keuper gypsum generally at excavated cross-section of 200 sq m to provide a three-lane highway in each direction. Each main face was split into seven sections with two sidewall drives excavated in parallel in advance followed by excavation and support of the crown section. The bench and base sections were then excavated and secured in half sections.
