Schieburg tunnel rockslide; Credit: CFL

Luxembourg's national railway company, the CFL, has announced that the traffic will resume through the Schieburg tunnel between Kautenbach and Clervaux after the Easter holidays in 2023.

On 27 August 2022, a rockslide occurred in the Schieburg tunnel between Kautenbach and Wilwerwiltz. The incident, which did not cause any injuries, occurred during a planned closure of the section concerned, in particular for the performance of maintenance work on the tunnel in question.

Consultive work to reopen the tunnel

Extensive geological and geophysical analyses was necessary to define a solution allowing the tunnel to be reopened under conditions that meet safety requirements. The objectives of the analyses, which required tweleve boreholes to be drilled from a depth of 50 to 75 metres, were to locate the cavity that occurred during the rockslide as well as to assess the stability of the mass of surrounding rock. Following the geological and geophysical analyses, a pocket of unstable rock mass with impressive dimensions (length: 20 m; width: 20 m; height: 25 m) has been identified. A hypothesis supported by the realisation of electrical and seismological tomographies. At the same time, several additional laser scans of the tunnel made it possible to rule out that its vault had been deformed during the rockslide.

Carrying out complex consolidation work in a very limited space

To allow the resumption of rail traffic, stabilisation both at the level of the pocket of unstable rock mass and at the level of the spill cone produced by the landslide is necessary. To this end, the rock debris covering part of the Schieburg tunnel track will have to be consolidated by injecting concrete grout.

Subsequently and through the boreholes created during the geological surveys, injections of expanded clay balls and concrete grout will fill the hollow spaces that were created when the rock collapsed. To allow the gradual clearing of rock debris inside the tunnel and ensure safety within the restricted space, temporary hangers are then installed.

Additional anchors are then applied to secure the elements injected into the altered zone of the rock with the healthy zone thereof. During the entirety of the works, the operations are checked on a regular basis. After the reprofiling of the vault, the rock debris is gradually evacuated and hangers installed. The supply of materials and special machines as well as the evacuation of the scree will be done via a temporary access whose installation was started directly after the incident.

Once the stabilisation and consolidation works have been completed, the railway infrastructure, including the tracks, will be checked and repaired as needed and the electric traction installations put back in place.

The phasing of the work described above ensures the safety of the employees involved throughout the operation.

The organisation of the work in the form of shift work as well as the request for exemptions from the collective leave of the trades involved allow rapid progress of the work despite the particularly restricted space inside the tunnel.

Continuation of alternative measures

The alternative measures offered since 12 September and reinforced on 3 October 2022 by the CFL, the Ministry of Mobility and Public Works, the Public Transport Administration and the municipalities concerned remain in force.

Substitution offer by CFL bus:

  • Ettelbruck – Clervaux: Frequency on weekdays: one service per hour in each direction, approximate duration: 42 minutes
  • Ettelbruck – Wilwerwiltz - Drauffelt – Clervaux - Troisvierges: Frequency during the week: one service per hour in each direction, approximate duration: 49 minutes between Ettelbruck and Clervaux. This bus also serves Troisvierges station
  • Kautenbach – Wilwerwiltz – Drauffelt – Clervaux: Frequency on weekdays: one service per hour in each direction, approximate duration: 34 minutes

At the same time, the Public Transport Administration will adapt, as soon as possible, the offer of RGTR line buses, among other things, with the aim of optimising the correspondence of the line buses concerned with the train.

Additional measures planned for the RGTR substitution offer:

  • Maintenance of temporary line 179 (Ettelbruck – Clervaux)
  • Maintenance of reinforcements on line 174 (Troisvierges – Hosingen) as well as extension of certain routes to Ettelbruck during peak hours,
  • Adaptation of timetables for lines 146 (Wiltz – Kautenbach), 147 (Wiltz – Goebelsmühle) and 153 (Wiltz – Kautenbach) to improve connections with the train.

This extended offer will be available until the reopening of the tunnel after the Easter holidays, from 17 April 2023.

All of the replacement measures and related timetables are available on the CFL website (cfl.lu) and on the CFL mobile application.