A25 Motorway Noise Barrier

Rotopile was called in for the foundations of a noise barrier on the A25, in Aveiro, on an embankment slope beside a motorway in full operation. The helical piles carry a reinforced-concrete capping beam, which in turn supports 3 × 3 m acoustic panels.

Heavy rain that winter degraded the embankment beyond what the geotechnical study had predicted, and the original solution, with vertical piles only, no longer held.

The answer was to drive the vertical piles deeper and add piles raked at 45°, working as anchors. Stability then came from the piles rather than from the condition of the fill. Sixty-three piles were used, in Ø127 × 9 mm and Ø88.9 × 9 mm shafts, 9 to 11 m long.

The work was done with one traffic lane closed for the machine, with no need for water or electricity at the working face. The crew was one operator and two helpers, and the schedule came in below that of a traditional foundation.

The job shows how the solution can be adjusted in real time when the ground turns out worse than expected, keeping the structure safe in difficult operating conditions.

63 helical piles · Ø127 × 9 and Ø88.9 × 9 mm · 9 to 11 m · 45° anchor piles · a crew of three