Civil Engineering May 2022 | Vol 30 No 4

Civil Engineering May 2022 5 Extensible reinforcements RESA’s extensible geosynthetic soil rein- forcing strips include: Q Q GeoStrap ® is made up of discrete chan- nels of closely packed high tenacity poly- ester fibres encased in a polyethylene sheath. It is suitable for backfills with high concentrations of salts and marine applications. It has a stiffness of 9 GPa. Q Q EcoStrap ™ is made up of compact bundles of polyvinyl alcohol (PVA-L) yarns protected by a polyethylene sheathing. It is designed to provide in- creased durability since it is not sensitive to the presence of salts in the backfill and is particularly adapted to applica- tions in which the backfill is potentially highly alkaline, as is the case with lime and cement-treated fills, or fills made of recycled aggregates containing crushed concrete. Moreover, EcoStrap™ does not show any sign of sensitivity to high tem- peratures. It has a stiffness of 21 GPa. The benefits of using elastic reinforcement extends to construction activities. It is delivered in rolls and is easy to handle and cut into convenient lengths on site, which are laced through a connection at the clad- ding. The straps are then tensioned over a trench and secured with a peg. The poly- ethylene sheath ensures efficient protection against damage during installation. These extensible reinforcements are imported to South Africa and should be assessed for quality and durability. Inextensible reinforcements High adherence, medium tensile, hot-dip galvanised steel reinforcing strips have a stiffness of 210 GPa. The HAR strips are ribbed, which mobilises the full angle of internal friction of the backfill. The shear plane is in the backfill on top of the ribs and not between the strip and the backfill, as would be the case for smooth strips. The HAR strips are thicker than the HA strips which allows more of the strip thickness to be allocated to strength and less to the sacrificial thickness required to meet the service life of the structures. The section at the end of the HAR strip is thickened and narrowed in such a way that the net section of the strip, after de- duction of the bolt hole at the connection, is greater than the strip cross-section. This ensures that the strength at the con- nection is greater than the strength of the strip and full elongation of the strip will occur before failure. There is no loss of strength when two HAR strips are joined with cover plates and bolts. During construction the strips are bolted to the cladding and laid out on compacted backfill. Rocky backfill will not damage the strips. The inelastic strips used in our struc- tures are all locally manufactured and exported from South Africa to the rest of the world. THE VALUE OF EXPERIENCE Reinforced Earth® should be considered as a material in much the same way that reinforced concrete is considered. RESA are experts in the understanding of the material and the design of MSE structures, but cannot design optimally without working together with project engineers and contractors. For more information www.recosa.co.za resa@recosa.co.za +27 (0)11 726 6180 Hot-dip galvanised steel reinforcing strips Internal stability – according to Reinforced Earth specifications Durability – designed for the required service life External stability – according to Reinforced Earth specifications Global stability – RESA works to- gether with geotechnical engineers Environment – RESA works together with environmental engineers