Civil Engineering October 2022 | Vol 30 No 9

32 October 2022 Civil Engineering S oil reinforcement is not a new concept; it has been around for thousands of years. The Great Wall of China was constructed using tamarisk branches as reinforcement. Today, geo- synthetics are seen as a cost-effective way to reinforce structures and improve the engineering characteristics of materials, allowing previously untapped areas to be developed, especially in road design. In both bound and unbound pave- ments, geosynthetics can be designed from below subgrade level as geocom- posite drainage, to glass fibre geogrids within the overlay of the road layer works. Additionally, geosynthetics can be designed to stabilise road embankments using high-strength geogrids as basal reinforcement. Rapid ageing and failure of road con- struction in bound layers occur when the pavements are exposed to repeated, high and focused loads. The behaviour of the road surface depends on the strength of the fill material and the subgrade below it, and roads should therefore be constructed on strong soil deposits (Ogundare et al., 2018). Good quality subgrade and fill material are not always available, and geogrids, geotextiles or a combination of geosynthetics can improve the proper- ties of the subgrade and fill materials. Appropriately designed and installed reinforcements placed within the road layers improve the performance of the road by extending its life, reducing the thickness of the layer works, increasing maintenance intervals, improving riding quality, and reducing cracking, rutting and distortions. South African roads are under severe pressure due to exposure of repeated, high, and focused loads. This exacerbates damage, reduces life span, and influences Geotechn i cal eng i neer i ng Layerworks in bound and unbound pavements Brandon Naidoo Commercial Civil Engineer Maccaferri The use of geotextiles and geogrids in road applications is quickly becoming an important design consideration in solving engineering and construction problems around the world. Between subgrade and insitu Woven/non-woven geotextile or geocomposite drain Basal reinforcement High strength geogrid Subbase/subgrade Woven geogrid Base course Extruded geogrid Wearing course reinforcement Steel mesh geogrid Asphalt reinforcement Fibreglass geogrid Figure 1 Geosynthetics used in layerworks Janita Ramanlal Commercial Civil Engineer Maccaferri