The Effect Of Geosynthetic Soil Reinforcement Design Standards On Costs For Earth-retaining Structures: A Qualitative Approach

The use of soil reinforcement in civil engineering applications is not new and in fact, this technology has existed for over 2000 years in the form of natural fibres used as soil inclusions in the Great Wall of China. Today, modern technology and science have developed soil reinforcement solutions that are consistent and mass reproducible. High tenacity polymers, with high molecular weight usually in the form of polyester or high density polyethylene are the most common materials used to achieve superior creep performance vital in earthretaining structures. Design standards in Australia and around the world are available to provide design guidelines in the specification and design of earth-retaining structures using geosynthetics. These include AS4678:2002 and BS8006:2010 as the official design codes. However, Government road authorities have published their own design guidelines such as the NSW Roads & Maritime Services R57 document and the Qld Main Roads MRS11.06 document to name a few. Different applications and loading conditions require different polymer types to get the maximum design benefits such as creep performance from polyester (PET) and high density polyethylene (HDPE), and installation damage resistance from polypropylene (PP) and HDPE. However, other installation and commercial factors may influence the preferred polymer type. This relates to issues such as; the ease of handling, cutting and unrolling of the product and of course even if it satisfies the design criteria, the cost of the product will ultimately determine if the solution is feasible. For permanent earthretaining structures, the two most common polymers used for soil reinforcement are polyester and HDPE. This paper will review two design codes adopted in Australia and how they impact on the feasibility (cost) of constructing a reinforced soil structure using geogrids.