CMA MEMBER INVOLVEMENT ENSURES BEST-PRACTICE STANDARDS ON MIDDELBURG RETAINING-WALL PROJECT:

CMA MEMBER INVOLVEMENT ENSURES BEST-PRACTICE STANDARDS ON MIDDELBURG RETAINING-WALL PROJECT:

Article Date: Wednesday 07 December 2011
Concrete Manufacturers Association (CMA) members were involved in every aspect of a concrete retaining block (CRB) wall project at Middelburg Mall, an ultra-modern regional shopping centre in Mpumalanga, which is due for completion in April 2012.

Several retaining walls were erected and completed in August 2011. They were designed as gravity retaining walls by Silvio Ferraris, CEO of CRB manufacturer and CMA member, ReMaCon, and were built against cut faces by CMA contractor member, Friction Retaining Structures, working as a sub-contractor for earthworks contractor, Protech Khuthele.

CMA director, Hamish Laing, says the CRB wall design complied with all CMA and SANS 207 requirements.

“The involvement of CMA members in the design, construction and CRB production aspects of the project has resulted in a well-built retaining-wall system which will provide many years of maintenance-free support.”

All the walls were built at an angle of 70º. The main wall is 433 linear metres long and four metres high in places. The remaining walls have a combined length of 270 linear meters and are all less than three metres high. 

Ground water below foundation level and the placement of electrical transformers above one of the walls had to be accommodated in the design. Standard drainage at the base of the walls was used to deal with the former. The drainage system was assembled using geopipes (perforated pipes) covered with 19mm of aggregate and encased in a Bidim A4 fabric.

Rock PC 50/50 geotextile reinforcement supplied by Kaytech, was used to anchor the wall below the transformers.

Laing says a gravity-wall as opposed to a geotextile-reinforced design was necessitated owing to the cut-faced embankments.

“Apart from the area immediately below the transformers, limited space precluded the use of geotextile reinforcement. Instead multi-layered skins were used to create the required additional mass and depth at the base of the walls. G7 minimum classification soil was used for the backfill areas and was tested using the DCP (Dynamic Cone Penetometer) method.”

All the blocks used on the project were supplied by CMA members. Envirowall blocks, manufactured by Technicrete and placed in a semi-closed-face configuration, were used for the front facing, whereas Remblock 30s and Terraforce L11 blocks, manufactured by ReMaCon, were used for the more economical open spacing layout on the unseen second section of the double-skin design.

Part of the main wall which is 433 linear metres long and four metres high in places.

PJ Doyer, project manager for civils and earthworks company, Protech Khuthele, seen here next to the main wall at Middelburg Mall.

One of the subsidiary CRB walls at Middelburg Mall.

DATE :  December 2011
ISSUED BY :  David Beer Communication Consultants
FOR :  Concrete Manufacturers Association
ENQUIRIES :  Hamish Laing (011) 805 6742
David Beer (011) 478 0239 or 082 880 6726.  Email: bigsky@ibi.co.za