Mechanical Stabilization Of Unbound Layers: Effect Of Geogrids On Low Strain Behaviour Of Granular Materials And Essential Characteristics For Optimum Performance In Permanent Roads

The use of geogrids in mechanically stabilized earth (MSE) structures and for trafficked areas over soft soils is well known. The essential characteristics of geogrids for MSE have well established over many years and are incorporated into national and international codes and standards. However, the mechanisms by which geogrids function in permanent roads and therefore the essential characteristics of geogrids operating at low strains in this application have often been disputed. This paper will present results from several recent research projects that identify the stabilization mechanisms that operate and identifies essential characteristics for geogrids in this function. A comparison is made between the stabilization function of geogrids and tensioned membrane reinforcement function of geogrids and the significance of this functional difference in the selection of essential geogrid characteristics for specification purposes. Such an understanding is essential if specifications are to protect designs that utilise the benefits of mechanical stabilization to increase pavement life.