Civil Engineering May 2022 | Vol 30 No 4

4 May 2022 Civil Engineering oN THE COVER A s with most successful inventions, Reinforced Earth® (RE) is a simple, yet effective material comprising only three elements: Backfill + reinforcing strips + facing Each RE structure is custom designed according to geometry, constituent materials, internal, external and global stability, durability, constructability and the environment. Keeping all these aspects in mind, it is essential that the RE structure that is integrated into a consulting engineer’s design is optimised to meet all the client’s technical and aesthetic requirements. Working upstream with project engineers, Reinforced Earth South Africa (RESA) offers early design input at no cost or commitment. The innovative solution-expertise that the Soletanche- Freyssinet Group provides to RESA through ongoing research and development is the basis for RESA’s success with MSE challenges in African conditions. GEOMETRY The RE structure is integrated into an earth fill and can be founded within the embankment. This leads to many possible geometric options. An embankment can be shaped into an optimum cross section. The geometry should allow access for earthmoving and compaction machinery throughout construction. BACKFILL The backfill is an integral design factor of any RE design and should be a frictional material – selected from locally available natural or commercial sources. The factors considered in the selection and specification of the backfill include the purpose and service life of the structure – the constructability, dura- bility of the reinforcements and the cost. REINFORCEMENT The specification of the reinforcements to be used is dictated by the unique characteristics of each project’s engineering re- quirements. The reinforcement options fall into two categories: 1. High tenacity geosynthetic fibres contained in a polyeth- ylene sheath (extensible reinforcements) 2. Medium tensile, hot-dip galvanised steel (inextensible reinforcements). Design considerations for Reinforced Earth® structures Reinforced Earth® is the trademark referring to mechanically stabilised earth (MSE) structures and has been producing load bearing retaining structures for countless solutions across the globe for more than 60 years. GeoStrap® reinforcing strips EcoStrap™ reinforcing strips