The first smart motorway was introduced in 2006 in the West Midlands and proved so successful that in 2007, Ruth Kelly, the then Secretary of State for Transport began a programme of further schemes beginning with two sections of the M6 at a public cost of £150 million.
In 2017 the upgrading of the 11 mile (18km) stretch of the M23 Junctions 8 to 10 near Gatwick Airport began and includes the extension to an all-lane running smart motorway, as it is the principal road link between London and the city’s second largest airport
The 164 million project carried out by Kier who, along with associated works, required a retaining wall solution for areas along the motorway. Hard shoulder conversions creating a fourth running lane were completed and installation of 12 Emergency Areas (EA’s) along with other associated works such as redefining junction layouts and creating new gantries for signage
The project includes retaining existing verges where possible and additional planting upon completion of the scheme to minimise views of the motorway. Much of the M23 between junctions 8 and 10 undulates between cuttings or embankment, so providing sufficient structural integrity to new running lanes requires significant earthworks as well as needing retaining walls.
Having worked with Kiers before and knowing that designs of retaining walls had to consider all the constraints associated with motorway construction, the Marshalls CPM Redi-Rock walling appeared to be best fit having already proved successful on several other smart motorway projects.
With junctions 8 to 10 being the busiest sections of the M23 with heavy volumes of traffic, associated slow-downs and phantom traffic jams that can occur even at off-peak times, Kier needed a resolution that is fast to install, and could be installed in any weather conditions. Redi-Rock walling offered additional health and safety advantages in places of high risk such as narrow lanes adjacent to busy motorways.
The easy to install Redi-Rock solution reduced section times as well as overall timescale period. Highways specific handrail blocks enhancing the safety of retaining wall were included to the top block during design and manufacture, stopping access from above. With a cobblestone finish preferred, each precast concrete block has the appearance of six smaller blocks on each face, giving a more natural stone looking finish whilst providing durability and strength.
Manufactured from over 25% recycled materials, the CE Marked, BBA approved Redi-Rock walling provides a sustainable solution that has approval from the Highway Authorities Product Approval Scheme (HAPAS) and a 120-year design life.