Two-layer lining for ÖBB railway tunnel projects with TBM / Ein- und zweischalige Auskleidung bei Tunnelbauprojekten der ÖBB mit kontinuierlichem Vortrieb

In the last 15 years, a number of transport tunnels for Austrian Railways ÖBB have been tendered for mechanised tunnelling by TBM and some have already been completed. The question whether to use one or two layers of lining was considered on practically all these projects. This either led to a decision which system to tender, or else the two alternatives were held to be equally suitable and the decision was left to market forces. These fundamental considerations about the lining system normally involved a systematic comparison and evaluation of the features of each system regarding the structural system (actions and resistance), serviceability (waterproofing, durability), the properties during and after a fire and operational and maintenance considerations.
The article explains:
- the essential system requirements concerning actions and resistance, serviceability and fire safety, with examples,
- the basic requirements for the operation and maintenance of ÖBB tunnels, including discussion of previous experience with maintenance,
- the basic features of single- or two-layer construction for continuously advanced tunnels, which are presented and briefly described,
- the system matrix used to make system decisions and the evaluation procedure,
- the economic considerations, mentioning the contrasting conditions in neighbouring European countries, including construction price and time considerations.
The system decisions or recommendations are analysed and argued through the example of rail tunnels in Germany and Switzerland as well as ÖBB tunnel projects. This overall treatment is intended to clarify how system decisions or recommendations were reached on ÖBB projects and what assistance can be derived for future projects, also considering foreseeable technical developments.