Coventry: M6 J2-4 Smart Motorway Scheme

DAWSON WAM was awarded the contract for the installation of permanent sheet piled retaining walls and plunge piles to allow for the M6 J2-4 smart motorway project to proceed in 2018. In total over 20 individual retaining walls were installed up to 20m in depth over an intensive 2 month period. Also 92nr isolated plunge piles were also installed using low ground pressure rigs for ROTTM, PTZ and RADAR foundations.

DAWSON-WAM utilised their powerful ABI TM22 piling rigs with revolutionary quick docking system which allows quick change over between auger drive and vibro hammer attachments saving 90% of rigging time which was key to the programme.

Piles were generally installed to significant depths into mudstone and sandstone with the strongest ground found to the Eastern half of the site. Preaugering was completed up to 20m into mudstone and sandstone to allow vibro installation of sheet piles. Preaugering was complete using the hybrid Cased CFA System which allows loosing of the hard mudstone/sandstone with relative ease compared to conventional CFA systems.

Sheet piles were installed using a powerful 30VV hammer which operates at ultra high frequencies reducing the damaging vibrations felt by lesser hammers and drive units.

A significant find of highly oxidated organic ground throughout the site meant that additional corrosion measure had to be utilised. DAWSON-WAM assisted the design team and BBV come up with a workable solution which allowed additional steel on the sheet piles to deal with the corrosion. Minor structural foundations for the ROTTM, PTZ and RADAR were also changed from driven tubes to plunge piles, encased in concrete and both galvanised and painted.

Due to the restricted nature of the works sheet piles and other materials for the retaining walls were delivered to DAWSON-WAM’s remote yard in Bedfordshire. From here piles were delivered to site on a just in time basis within traffic management restricts to minimise disruption of other works and the public. Piles were purchased by DAWSON-WAM.

AS part of our quest for continual improvements we continued trialling our smart barrier system on the project. This smart barrier works alongside conventional systems and alerts operatives to anyone or anything breaking the barrier. The success of the system meant that BBV recommended the use of the system to other subcontractors with a view to making it mandatory in further works.

The project was completed using the BIM compliant Business Collaborator software. Both our clients and our own integrated management systems which were adhered to and audited under ISO9001, ISO14001 and OHSAS18001

During the course of our works we were involved in liaison with our client, Highways England, and other associated bodies in weekly review meetings and design development meetings.

DAWSON-WAM undertook the scheme under the goals set out in its sustainability policy and matched the requirements of the BBVJV sustainability plan and diversity plan for the scheme. The M6 was classed as an environmentally active and sensitive area and strict protocol’s were put in place to ensure as little disruption to as possible to the natural environment and wildlife. We installed piles beside watercourses and badger habitats, as well as adjacent to live Network Rail infrastructure, critical utilities and sensitive structures.