Concrete segments for tunnels

Reinforced concrete ring stones form the lining of tunnels excavated using ribs and breast boards.

The structural design takes into account all the strains they will be subjected to. This starts with the form stripping, followed by the handling, storage and installation stages, then an analysis of the thrust produced by jacks and finally at the entrance of the loads exerted by the land on the ring stone.

The size of the rings formed by seven stones manufactured at our facilities in Humanes, Madrid are:

  • Inner diameter: 8,430 mm
  • Outer diameter: 9,070 mm
  • Length: 1500 mm

The segments that form the ring have different geometries depending on their position in the ring. These segments are assembled in the tunnel sheltered by the shell of the breast board by fitting them together, bolting the circumference and radial joints with high-strength straight bolts housed in recesses built into each segment.

Completed Projects

To date our facilities have produced 40,000 metres (more than 26,600 rings), which makes a total of 186,000 segments and 26,000 auxiliary track support pieces, for the following projects, among others:
For the extension of Line 2 of the Madrid Subway to Las Rosas, a total of 4,000 metres were built between 2009 and 2010.
For the Metrosur line, 4,011 metres (2,674 rings) and the same number of track support pieces were manufactured over the years 2000 and 2001.
For the Alcobendas (Madrid) branch line, 1,650 metres (1,100 rings) and an equal number of track support pieces were built between March and August 1999.
For the Madrid Airport line, 3,555 metres (2,370 rings) and the same number of track support pieces were manufactured between March ‘98 and January ‘99.
For Line 7 of the Madrid Subway, a total of 3,294 metres (2,196 rings) and the same number of track support pieces were manufactured between March ‘97 and January ‘98.