Gleinalm Motorway Tunnel – 2^nd tube logistical challenges / Gleinalmtunnel – Neubau der zweiten Röhre

Abstract

In 2013 Asfinag published the tender for the construction of the second tube of the Gleinalm Tunnel. The tunnel is situated in hard rocks (gneiss) and the tender design contained excavation works realized by "drill and blast" in a top heading, bench and invert sequence. Additionally to this tender design, technical alternatives were allowed. One of the tenderers, the later contractor, offered both, a concept according to the tender and an alternative excavation concept including full face excavation by drill and blast. This alternative was based on considerations and experience the tenderer had gained from the construction works of the first tube in the early 1970s presuming optimal full face excavation conditions over wide areas of the tunnel and thus reducing time and costs. Due to these economic advantages and the low cost risk the owner finally commissioned the alternative. Minimizing the blasting vibration of the full face excavation on the nearby running tube, which was operated without any disturbance, was only one of the challenges of the project. In terms of logistics the supply of the excavation works with air and support materials as well as the huge mucking volume to be transported were identified as limiting factors.