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In accordance with traditional systems, the execution of underpasses and structures under railroad tracks entails a series of determining factors and additional works that can lead to major setbacks during the railway operations.

The jacking method can be used to build and assemble the full structure out of the tracks platform. An excavation phase and a transport phase will then be required to place the structure in its final position.

The concept of this system is very simple and the railway system is not affected by additional processing times for the set-up of the structure at the site.

It is applicable to road and railway underpass jacking solutions.


Description of the process

Construction of the structure

The operation starts with the construction of the structure near the embankment where the jacking operations are going to be executed. The structure is built on a fully horizontal surface or sliding bed, which is covered with a polyethylene surface to prevent the adherence of concrete. Likewise, a series of lateral guides are built on the sliding bed to control the direction and movements of the caisson on the bed and the reaction wall that will be pushed by the hydraulic jacks.


Bracing of the track

The track must be braced before carrying out the jacking operations, with the use of special braces that can be used to form rail bundles, with enough resistance for trains to travel at a speed of 30 Km/h.


Introduction of manoeuvre beams

The next step involves supporting the tracks with very large metallic profiles that can transfer the efforts of the track to the caisson. These profiles are supported between the caisson and the terrain first, until the advance length is enough to make sure that only the caisson can be supported.

At this point, the manoeuvre beams are strapped to a cross girder, which is then strapped to a fixed point to prevent the relative displacement of the track.


Excavation

This is a cyclical task that takes place before the launching activities. The terrain typology is fundamental to achieve different performances.


Oleodynamic launching

The structure is launched with hydraulic jacks. The plunger of the hydraulic jack thrusts backwards and it pushes the reaction wall, pushing the caisson forward.

The hydraulic jacks retract at the end of their travel and a metallic separating element is installed to act as support for the new hydraulic jack.

The cycle is repeated until the daily launching time has expired. Next, all metallic separating elements are removed to extend the reaction wall in a length equal to that pushed with the use of concrete pouring operations.

Finally, the cycle is repeated every day until the caisson is in its final position.

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