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The new approx. 21 km long section between Köstendorf and Salzburg is one of the last major milestones in the upgrading of the Salzburg–Vienna rail corridor to four tracks. The section comprises a multitude of different civil engineering structures, posing high demands on the interdisciplinary design team. The open sections of the alignment require many over‐ and underpasses and road diversions. In addition, the majority of the section runs underground through the Flachgau Tunnel, which has the particular feature of a tunnel bridge. The aim of the BIM project is to provide a software‐independent, integrated model of the whole project. All parties involved in the project collaborate to define the LOD for the terrain, existing building, land use and geological models, as well as the models for the proposed new infrastructure for the open section, tunnels, ventilation control building, bridges, civil structures and drainage. The LoD are defined in parallel with the AIA according to the KISTE infrastructure identification system used by ÖBB (Austrian Federal Railways). At the same time, the BIM execution plans are generated by the team and adapted to the new BIM processes. The opportunities provided by the element‐based display and evaluation are anticipated to lead to considerable improvements in the field of interdisciplinary design and visualisation studies. The present article describes the current state of work and provides a preview of future developments.

After the completion of the route selection process for the ÖBB New Semmering Base Tunnel rail project, a geological, hydrogeological and geotechnical investigation programme was developed for the chosen "Pfaffensattel" route and implemented in 2008/2009. The programme included drilling cores with an extensive programme of geophysical, geotechnical and hydraulic borehole investigations, geophysical measurements on the surface and laboratory testing to determine geological, hydrogeological and geotechnical parameters. The results of this investigation programme and the knowledge gained form the basis for the specialist contributions for the production of the environmental impact assessment and also the documents required for the application under the Railway Law. Starting situationThe route selection process found the "Pfaffensattel" route with portals at Gloggnitz in Lower Austria and Mürz-zuschlag in Styria to be the best variant for the construction of the New Semmering Base Tunnel (SBTn). In order to investigate the geological, hydrogeological and geotechnical conditions along the selected route as part of the partially concentrated approval process under to clause of the Railway Law 1957 and EIA Law 2000, an extensive investigation programme was developed by the appointed consultants in winter 2007/2008 and then implemented in the period 2008 to 2009. At the time of writing this article, the evaluation work required for modelling the geological ground conditions was largely completed; the evaluation of the geotechnical and hydrogeological investigations was still underway.

Since the start of construction on contract SBT3.1 in May 2016, all three tunnel construction contracts for the Semmering Base Tunnel are now under construction. From the geological and geotechnical point of view, this represents the transition from the geotechnical prediction for the design for tendering to the documentation in the course of construction. The paper describes the considerations about the systematics of ground characterisation and the definition of ground types in the course of producing the ground prediction for the design for tendering. It also describes the requirements for the documentation of ground conditions encountered during the advance, the updating of the prediction for the daily specification of support measures and the comparison of prediction and actual conditions for contractual purposes.

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