The new railway line between Köstendorf and Salzburg – Looking back to the past and forward to the future

Abstract

AbstractTo increase capacity and reduce travel time for long‐distance traffic, the Austrian Federal Railways (ÖBB‐Infrastruktur AG) are planning a new railway line between Köstendorf and Salzburg. The centrepiece of the project is the Flachgau Tunnel – an approx. 16 km long, twin‐tube single‐track tunnel system. The selected tunnel alignment ‘'K5 optimiert'' was developed in a multi‐year route selection procedure. Further optimisation within the current design stage – the detailed submission – achieved a 200 m shortening in tunnel length. The chosen standard cross‐section was substantiated with life‐cycle‐cost and carbon‐footprint investigations which also coincided with experiences from the construction and operation of existing tunnel structures with varying cross‐sections and travel speeds. Both studies show the advantages of the larger 54 m2 cross‐section compared to a smaller 44 m2 cross‐section. Complex hydrogeological conditions require a water pressure‐tight tunnel design capable of withstanding a maximum pressure of approx. 11 bar. These conditions are especially challenging for conventional tunnelling methods and require a waterproofing concept with two independent sealing layers. At present, the construction of the project is scheduled to take place from 2027 until 2040.