Renewing the tracks on the Llobregat-Anoia line owned by the Catalan railway company Ferrocarrils de la Generalitat (FGC), Barcelona

The kilometres in and around L’Hospitalet de Llobregat on the Llobregat-Anoia line need to be modified to replace the current ballast with concrete slabs. Work can only be carried out on the track being replaced when it is out of service, requiring crews to work non-stop, 24/7, including holidays. 

With regard to the track kept operational, FGC will run a night-time service to load and unload materials, auxiliary equipment, tools and waste. This requires extensive planning in terms of logistics. 

Before starting work, a Wellpoint system needs to be used to dewater the area, which will consist of 24 pumps and 8 pressure gauges to monitor groundwater levels in real time.  

This is a two-stage process, with each track replacement representing one stage. Work is carried out inside tunnels on both sides of the station. At night, the track is taken out of service, and the rails on the track being replaced are lifted and removed. Then the ballast bed is stripped, and metal formwork is applied to retain the ballast shoulder and stop the adjacent operating track from becoming uneven. 

To continue working on the track taken out of service during daytime, a metal clearance safety barrier is installed to ensure crews can work safely. 

Day crews will clean the concrete slabs where the ballast was cleared, and attach the connectors flush to the existing slabs using 20 mm rebar through rotary-percussive drilling and epoxy resin. 

Afterwards, any cracks or crevices found on the slab are repaired with staples or injected with resin and defects are corrected using high strength grade mortar. Day crews attach connectors to core walls using rebar, drilling and resin, and injection pipes and a hydro-expansive profile are laid down to waterproof the inverted arch. 

The structural slab is then reinforced and formwork is applied along the shoulder. Once this is complete, it is primed with binder resin and concrete is poured for the new slab. After the new track is assembled and level, binder resin is used for different aged concrete, and concrete is poured for the track slab using MC-40 fibre-reinforced concrete. Finally, the rails are welded, and once the concrete reaches the strength needed, the track is put into service and the other track is taken out of service. 

The work for the second phase will be the same, but the safety clearance barrier will need to be modified and placed on the shoulder of the phase 1 track’s slab in order to reinforce the structural slab.