M25 ERA bay 12

Bay 12 was our largest single EA bay project. The design included a 130m long pre-cast concrete L-shaped retaining structure up to 2.5m high at the base of the embankment.

The foundation was constructed of 400mm thick reinforced concrete of varying width and level. 150m3 of concrete was pumped 160m from the carriageway to the foundation.

The L-shaped wall was installed using two large excavators in a two-part lift to be as efficient as possible. The sections were then lifted from the road to the middle of the stepped embankment, then an excavator 6m below the carriageway at the foundation level continuously installed wall sections unimpeded.

Whilst the structure was being installed, we proposed the use of a ‘deckdrain’ back-of-wall drainage system to save time on installation. The embankment was filled with over 5,500 tonnes of structural fill.

This bay was completed before the Christmas embargo in December 2020.

Skanska’s works manager commended our teams:

“Your site teams are producing an excellent job despite current conditions and restrictions. The sites were in excellent condition and all H&S measures were being employed. The gate operative was courteous and informative. I felt the team was creating a positive impression with the travelling public.”

Skanska’s senior engineer emailed to say their health and safety adviser was “impressed with how the site is set up, measures in place, PPE compliance and generally how it presents itself.

“The engineer asked us to relay these positive comments to the site team, and thank them for the hard work in this very difficult time.”