Dimensioning Fire when Designing the Steinbühl Tunnel

Based on the Deutsche Bahn guideline (RiI) 853, verification of computational fire protection was undertaken for the inner shell of the Steinbühl Tunnel. Initial calculations had revealed that in order to confine concrete spalling, a non-contractual procedure calling for the application of a concrete mix with PP fibres would be required. As a result, additional computational verifications for fire incidents were undertaken on the part of the client as a “second opinion” for the case of fire. This culminated in proving that the inner shell can indeed be verified without PP fibres being applied by taking advantage of possible optimization factors.

1 Introduction

The „Albaufstieg“ as the central section of the new Wendlingen–Ulm rail line – part of the major Stuttgart-Ulm project – starts with the 8806 m long Boßler Tunnel, which is linked with the two Filstal valley bridges. The Albaufstieg section concludes with the 4847 m long Steinbühl Tunnel [1].

The Steinbühl Tunnel, which is devised as a twin-tube structure for safety reasons, begins in the Filstal at Mühlhausen in the valley at a height of 642 m ASL. Then it rises from the Todsburg portal with a grade of 17–24 ‰ by 105 m to reach a height of 747 m ASL (Fig. 1).

The tunnelling work...

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