Seven years after the completion of a new boundary-wall retention structure for the Italian embassy in Ethiopia, the solution has proven to be structurally durable and environment friendly.

South Africa-based solutions provider for the civil engineering and construction market Maccaferri provided its Green Terramesh technology for the Italian embassy in Ethiopia in 2006. The service included engineering, procurement and site assistance for the project.

The embassy is located on a hilltop, at an elevation of 2 500 m above sea level. In 2005, the slope became unstable because of surface erosion and shallow slips and the nearby river also undermined the stability of the slope because of erosion during heavy rains. If these factors had continued, it would have led to the collapse of the boundary wall.

Also, the elevation of the site of the boundary wall was not conducive to the growing of plants, but the Green Terramesh solution has made the growth of shrubs and grass through the face of the wall possible.

Maccaferri’s initial design focus was to prevent scouring at the toe of the wall by building a flexible, rock-filled mattress. Secondly, the Terramesh permeable soil reinforcement was inserted at the foot of the slope. This system’s front portion acts as a free-flowing drain because of the highly porous rocks. Compacted backfill made up of double twisted and poly- vinyl chloride-coated wire mesh was then positioned on the reinforcing elements.

Finally, an environment-friendly, flexible soil reinforcement product was used to retain most of the slope. The Green Terramesh provided the cost-effective solution using local backfill materials.

It was also necessary to divert the uncontrolled surface drainage from the slope through a lined channel and around the retaining walls to ensure that the backfill remains dry. This was achieved using Macmat-R, a geocomposite product made of double-twisted steel wire mesh and a co-extruded polypropylene mat, which reduce the velocity of the running surface water, while allowing vegetation to grow through the apertures of the synthetic mat.