ABSTRACT:

The 57 km long Gotthard Base Tunnel is the core of the Gotthard Axis which is part of the New Railway Alpine Transversal (NEAT) through the Swiss Alps. During the construction of the multifunction station (MFS) at the section Faido at a depth of 1240m a large, not prognosticated fault zone system was encountered. Its impact on the layout of the MFS Faido is described and the excavation procedures and the rock support measures as well as the extensive geotechnical computations are explained. After coping with the challenges of the difficult geology and the complex layout the MFS Faido was completed successfully. This was accomplished due to close cooperation between the Alp Transit Gotthard Ltd., the Engineering Joint Venture Gotthard Base Tunnel South and the contractors.

1 INTRODUCTION

The 57 km long Gotthard Base Tunnel (GBT) is a key part of the Swiss high speed railway line through the Alps. The designed maximal train speed is 200 to 250 km/h so the route must be constructed as a flat railway with gradients no higher than 1%. The GBT will be the world's longest railway tunnel and put into operation in 2017. The GBT contains two single-track tubes and two multifunctional underground stations in the construction sections of Sedrun and Faido. The MFS Faido consists of the single-track tubes, two tunnel cross overs with four trumpet-shaped tunnel branch-off structures as well as emergency stations, ventilation channels and shafts. The multifunction station comprises a total of 9 km tunnels and galleries. The cross cavern lays at the end of the access tunnel. It is perpendicular to the two single-track tubes and houses vital facilities for the construction of the whole project and the tunnel operation (Fig. 1). During the construction of the cross cavern a fault zone system was encountered.

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