The Carbayín is located at kilometre 28/634 on the Gijón Sanz Crespo – Laviana 752 line on the metric went network, with a section 4 a single lane electrified track, with a length of 1039 m.
A prior analysis of the issues detected took place via a visual inspection, and in function of these the following reinforcement works took place with the aim of re-establishing the tunnels safety and stability:
- Damp and water leaks of the arch and gables: A watertight sheet was installed in the tunnel to allow infiltration water drainage from the key to the gables in order to prevent it landing on the overhead cables and track. In addition, where a constant flow of water was detected, a putlog hole was installed which allows rapid water drainage.
- Cracks and falling cement landing on the gables without trusses: Treatment consisted in extending the trusses in the excavated area until reaching the base of the tunnel. For this the affected area was prepared and then an excavation truss was installed with pins, to finally projector concrete onto the treated area.
- Flaking and falling projected cement on rock or Bernold sheet. The sheets and trusses are manually brushed to get rid of any rust and parts that are worn by rust in order to then project the cement.
- Missing coating of the Bernold sheet. Once the metallic sheets and trusses are brushed, those that were very worn were replaced for new ones. The cement was then projected into the recesses.
- Cracks and falling projected cement and rock on the arch.
In this specific case, the whole section of the tunnel was treated, consisting in the installation of metallic trusses and anchored with pins to the rock substrata, along with the installation of Bernold sheets between them. Along with the cement filler in the space created between the rock and the Bernold sheets, culminating in the treatment with projected cement onto the trusses, pins and Bernold sheets.