Albabstieg tunnel

The 6,800 m long section of the NBS Wendlingen-Ulm mainly consists of the two single-track tubes of the Albabstieg tunnel, each approx. 5,880 m long, which are connected by 11 cross-passage structures.

The excavations with an excavation volume of 1.2 million cubic meters were carried out using the shotcrete method from 2 points of attack in parallel in both tubes: from the north portal Dornstadt in the direction of Lehrer Tal and from the intermediate attack Lehrer Tal in the direction of Dornstadt and to Ulm. The tunnel was lined with plastic sealing sheets and an in-situ concrete inner shell 40 and 50 cm thick.

In addition to the execution planning for the overall measure, the 50 m long cut-and-cover construction at the Dornstadt portal as well as civil engineering and sewer construction work for the railroad line on a 950 m long open section including two large earthworks with a total volume of 550.000 m³ as well as extensive sewer construction work in the Dornstadt portal area.

Geology/hydrology

Massive and stratified White Jurassic formations predominate, as well as overlying bench limestones and the cement marl formation.
The area near the portal lies in the Lower Freshwater Molasse.

As karst phenomena were likely to be encountered in the White Jurassic, an extensive exploration program with boreholes around the tunnel cross-section was carried out during the drive. During the excavation, karst vents filled with sediments of varying thicknesses and a large karst cave were encountered. The tunnel is not in groundwater, but was designed for a water level between 0 and 15 m above the tunnel roof.