Geology & Tunnel

Cross-border tunnel through the Ore Mountains

The new railway will enable fast, convenient travel between Dresden and Prague with an at least 26 km long, cross-border tunnel through the Ore Mountains. Get to know the Erzgebirgstunnel and find out how geological studies help us to plan it.
Many core drillings lay in two rows next to each other, each in a wooden basket.
Drill core bearing. DB AG / Natalie Klein
Szene from drilling with drill cores in the front of the picture. In the back are workers in high-visibility vests, heavy machinery and construction fences. It a sunny day with some clouds.
Drilling campaign. DB AG / Jan Frintert
On a sunny day, two workers in high-visibility-vests are in the process of core drilling at a drilling construction site.
Drilling campaign. DB AG / Jan Frintert

Going deeper. A window into the ground

The new line runs through an area with complex geological and hydrogeological conditions. Therefore, close cooperation between the responsible authorities in Germany and Czechia was essential right from the beginning. 

Geotechnical investigations help us to better understand the composition of the ground. We drill up to 500 meters deep. The boreholes provide insights into the rocks, geological fault zones and fissures, as well as the conditions and composition of the groundwater. We also study the mechanical and chemical properties of the ground. To do this, we collect unconsolidated and solid rock samples from the borehole for geotechnical laboratory analyses.
 

Experience and understand

The subsoil investigations also help us to suggest the most appropriate measures to prevent groundwater subsidence or, conversely, to drain surface water away from the future track. The results will also indicate whether measures need to be taken to prevent structural noise from propagating through the bedrock.

When planning the exploration measures, the project teams collected extensive geodata from archives and publications in Germany and the Czech Republic. These were manufactured into a digital three-dimensional ground model to be used for Building Information Modelling (BIM) which is an integral part for the initial planning of the route. Find out more about how we are planning the new line and the tunnel using the latest BIM technologies.

Technology & Innovation

Drilling campaigns for the tunnel

To investigate the subsurface conditions, intensive test drillings were carried out in Germany and in Czechia.

During two drilling campaigns (June 2020 – November 2021 and November 2021 – July 2023), subsurface investigations were conducted at selected points along the existing line and in the study area. The focus of the first drilling campaign was to characterize the fault zones that the German geologists had predicted with six vertical and three inclined core drillings of up to 400 m. The boreholes were planned and positioned using a 3D geological model and digital maps. The aim of the second drilling campaign was to expand our knowledge about the ground. For this purpose, more than 20 additional core drillings with drilling depths of up to 500 m were carried out in the study area north of the state border. It took about a month to drill 100 m deep.

There is a need for more in-depth investigation in the area close to the border, where all route options converge and cross the intersection of the Gottleubatal zone with the Petrovice-Döbra structure. Building a tunnel through the Krušné hory fault zone on the southern edge (Czech side) of the Ore Mountains is a particular geotechnical challenge.

The heart of the project: Erzgebirgstunnel/ Krušnohorský tunel

To allow the new line to overcome the Ore Mountains (Erzgebirge) on the German-Czech border, a cross-border base tunnel is required. The tunnel will be at least 26 km in length, with at least 14 km on the German side, which makes it Germany’s longest railway tunnel. The tunnel will be built as a pair of single-track railway tunnels to ensure mixed passenger and freight operations. The predominant rock here is gneiss, typical for the Ore Mountains. 

Get to know the Erzgebirgstunnel

The Erzgebirgstunnel is being built with two parallel, single-track tubes that are connected to each other every 500 m maximum via connecting structures. The tunnel wall is made up of shell-shaped concrete segments (so-called tubbing construction method). In some places, the tunnel runs up to 600 m deep below the surface!

Tracks accessible for traffic vehicles in a clean, new tunnel, with white and blue lightning.
Tracks accessible for traffic vehicles of tunnel in Bad Cannstatt, Germany. DB AG / Arnim Kilgus

A drilling machine for the new railway line Dresden – Prague

A tunnel boring machine specially made for the project “excavates” the tube and then assembles the tubbings into rings. At Seidewitz, a tunnel access for the machine is built, a so-called intermediate incision. From there, the tunnel boring machine works its way into both directions – this keeps the intervention at the tunnel portals as minimal as possible. We check the rock that the machine loosens from the subsoil immediately for possible reuse in the project.

A model of a drilling machine at the info centre in Heidenau, similar to the one that will be used for the Erzgebirgstunnel.
A model of a the machine is displayed in the Heidenau information centre. DB AG / Jörn Daberkow

Beyond tracks and tubes: A network of structural safety facilites

In addition to the tunnel tubes and tracks, the Erzgebirgstunnel consists of many structural facilities: It is a system of connective structures, parallel tunnels, rooms and paths that are essential for fire and disaster protection. The off-road access points to the tunnel are connected to the public traffic system. Near Göppersdorf, we are building an additional evacuation and rescue site, which is connected to a rescue tunnel between the tunnel tubes about halfway along the route.

A visualisation of the evacuation and rescue site Göppersdorf for the new line Dresden - Prague.
Position of evacuation and rescue site with access to rescue tunnel near Göppersdorf. DB AG