Fachinger & Cramberger Tunnel, Limburg an der Lahn

Over the next few years, Deutsche Bahn will be renewing six tunnels on the Lahntal railway between Wetzlar and Koblenz. On behalf of Deutsche Bahn, PORR is renewing the tunnels in a consortium with FELDHAUS Bergbau GmbH & Co. KG and Heinz Schnorpfeil Bau GmbH to renew the first two lots: Fachinger Tunnel and Cramberger Tunnel. The cross-sections of the structures need to be widened in order to fulfil current regulations. The tunnels are being widened using the tunnel-in-tunnel method under a rolling wheel. 

Tunnels from pre-imperial times

Between Diez and Nassau, the Lahn winds its way through the landscape in narrow loops. For the most part, the double-track Lahntalbahn railway follows the course of the river; only in some places does the route branch off through tunnels, most of which were cut into the rocks of the Rhenish Slate Mountains in the 19th century. Both the 426 metre long Fachingen Tunnel between Diez and Fachingen and the 732 metre long Cramberg Tunnel between Balduinstein and Laurenburg were put into operation in 1862. As they show considerable signs of damage, they need to be structurally renewed after 160 years of operation.

Tunnel renewal under rolling wheels

The existing tunnel cross-section must be widened in order to guarantee the prescribed clearance gauge. In addition, space must be created in the Cramberg Tunnel for lateral escape routes. Furthermore, the track spacing must be increased to 4 metres. The listed portal structures of the Cramberg Tunnel will be demolished and replaced by portal structures that will be modelled as closely as possible on their historical counterparts.

Parts of the old tunnel portal, which is well worth seeing, are to be secured and possibly erected in the neighbouring communities. As years of closure of the railway line, which is very important for rail commuters and tourists, is out of the question, the work will be carried out while the railway is restricted to one track. For this purpose, the existing tracks will be dismantled and a new track built in the centre of the tunnel.

Construction using the "tunnel-in-tunnel method" (TiT method) in cyclical tunnelling

In order to widen the tunnel cross-sections, "Nora" and "Tilly von Cramberg" work their way 426 and 732 metres through the mountain respectively. The existing structures are being dismantled with the help of the two mighty tunnelling portals. Cuts with soil nailing and partial net support will be created at the portals. Once the existing brick vaults have been completely dismantled, a horseshoe-shaped inner shell made of waterproof C35/45 concrete with high sulphate resistance will be constructed. It consists of foundations and an inner shell on top. The expansion is carried out by chiselling and blasting the rock. Anchors as well as a reinforced shotcrete shell, also of grade C35/45, are used as securing means. Rail traffic will continue to run safely on the newly laid track in the centre of the existing tube under the protection of an enclosure during the entire construction work.