Analysis And Design Of Geogrid-reinforced Unbound Granular Pavement Over Soft Subgrade For Low Volume Roads

Unbound granular pavements (UGM) are extensively used in low volume roads in rural Australia due to their low cost and availability of local materials. In areas where the subgrade support is of low strength (CBR < 3%), it is recommended to improve existing soft subgrade by stabilisation or by replacing it with better quality selected subgrade materials or by using geosynthetics. Even though current pavement design practices in Australia mention the use of geotextiles as a possible ground treatment option to expedite construction and to assist in compaction of subsequent pavement layers, they do not consider the benefit of using geosynthetic reinforcements to enhance structural performance. Consequently, pavement design procedures and charts are not available for such cases. This study uses two-dimensional (2D) axisymmetric finite element model (FEM) to analyse the behaviour of geogrid-reinforced UGM pavements over soft subgrades. The critical pavement responses such as vertical surface deformation, compressive strain and compressive stress at the top of subgrade are simulated numerically using a commercially available FEM program ABAQUS. The model is verified using published literature-based information. FEM results are then used to develop design charts which can be directly used in practice. These design charts would help pavement practitioners to evaluate the cost-effectiveness of geogrid-reinforced UGM base over conventional unreinforced granular base.