Engineers at Dudley MDC came up with a novel solution when replacing an unstable, 100 year-old brick retaining wall in Stourbridge, West Midlands. The wall, built within a densely packed residential area, formed the lower 2.5 -3.0 m of a 7m high embankment separating two streets. Over the years, the wall had suffered significant horizontal and rotational slippage and was in imminent danger of failure.

 

Although legal ownership of the wall was in doubt, Dudley accepted responsibility for the structure and designed a radical, masonry-faced, piled retaining wall solution, which satisfied strict engineering criteria as well as aesthetic requirements.

 

Main contractors, Wrekin Construction installed a 150m long series of 600mm diameter rotary-augred, cast in-situ piles. Each pile was 10-12m long set 4-5m below ground level. The wall was then faced with MacWall Landmark, masonry retaining wall blocks.

 

MacWall retaining wall blocks usually form part of a composite, reinforced earth structure that uses geosynthetic grids and compacted backfill to form highly efficient retaining walls. For this project, the walling was specified more for its ease and speed of construction as well as its attractive masonry appearance.

 

Explaining this decision, Dudley MDC Section Engineer, Roger Morgan said, “The MacWall Landmark system was chosen after consultation with Wrekin and local residents. The facing had to be aesthetically pleasing as well as easy to install. The site had severe access restrictions so we needed a walling that could be built by hand with the minimum of plant”

 

The MacWall Landmark wall was built by specialist sub-contractors, PC Construction. Blocks were tied back to the piled structure using U-shaped stainless steel anchors. The blocks were dry laid without mortar and the void between wall and piles filled with free-draining no-fines concrete. Drainage was provided at the base of the wall to prevent the build up of hydrostatic pressure. The wall was then capped with purpose made coping units. These butted up to the pile capping beam which also carries a protective guard rail.

 

Because of the restricted access to the site, the MacWall Landmark blocks were craned in from above to allow installers to move them to the required position.

 

Roger Morgan added; “This was a complex project and we are delighted with the result. The MacWall Landmark system has given us an added bonus of reducing the overall footprint of the wall. The road at the foot of the wall is now 1m wider than the original making access for residents much easier than before”

 

The £750k, Stourbridge project began in October 2006 and was due for completion in September 2007.