Mechanical stabilization of unpaved sand roads on fraser island

Abstract

Degradation of the road surface quality of the unpaved sand roads of Fraser Island, Queensland, a World Heritage Listed site, occurs because of two major factors. The first is the combined impact of surface runoff from storm events causes water erosion of the road surface, and second is the impact of vehicle tires causes lateral displacement of road surface material. Both processes result in removal of sand from the road surface, a gradual lowering of the elevation of the road surface relative to the surrounding natural forest environment and severe degradation of the road surface. The transported sand blocks stormwater drainage paths and the removal of sand from the road surface results in road closures and reduced access to tourist sites. Mechanical stabilization of the sand pavement is a technique that can assist in minimizing sand loss from the road surface. Laboratory testing of bentonite stabilized sand by varying the percentages of bentonite and moisture content within the sand mixes was undertaken. The effectiveness of bentonite as a sand stabilizer was measured against criteria including optimum bentonite content, optimum moisture content, suction, permeability and CBR. Results obtained to date, indicate that bentonite can significantly improve the load bearing characteristics of the unpaved sand roads. Stabilization of the sand roads using bentonite and compaction, may thus provide a low cost option to increase the bearing capacity of the sand roads in this sensitive environment and thereby provide a sustainable road network in the long term.