THEextension of Line 3 from Ethniki Amyna to Plakentia runs through a densely-populated area, and some sections of the tunnels were bored beneath residential buildings or other structures. An elastically-supported trackform was specified to help minimise ground-borne vibrations.
Attiko Metro awarded the trackwork contract to Stedef and Sateba, specifying the use of twin-block sleepers, rubber mountings and resilient pads. In addition to material properties such as water absorption and resistance to rail creep, the specification for the insert pads required a static stiffness of 13 to 22N/mm and a dynamic stiffness of 23 to 37N/mm. Each pad measures 660 x 230 x 12mm.
After exhaustive tests, Attiko Metro decided to adopt Sylomer insert pads supplied by Getzner. The tests included an assessment of residual deformation 24h after the load had been removed, and permanent deformation. This was limited to a maximum of 35% of the original thickness, but the tests found that permanent deformation of a Sylomer pad was less than 3%.