The work, which will maintain safety for road users, will be carried out north of the western bore of the tunnel.
Graeme Steward, Highways Agency Project Sponsor said:
Safety is a top priority for the Highways Agency and this scheme, to upgrade the barrier alongside the northbound carriageway, is part of our commitment to that.
We have planned this work carefully to minimise disruption for road users. That is why work will only take place overnight, when traffic flows are at their lowest, and not on Friday or Saturday nights. To allow the work to take place safely, and for the protection of our road workers, we will need to close the western bore of the tunnel and lanes one and two for a short distance on the northern side of the tunnel. Traffic will still be able to exit at junction 31.
The work will begin on Sunday 2 March and will finish in the morning of Friday 28 March, with no work taking place on Fridays or Saturdays. All work will take place between 8.30pm and 5.30am and traffic will be able to pass the work in the eastern bore and lanes 3 and 4.
Members of the public should contact the Highways Agency Information Line on 0300 123 5000
Journalists should contact the Highways Agency press office on 0844 693 1448 and use the menu to speak to the most appropriate press officer