Anchored and Pre-tensioned Geosynthetics in Unpaved Roads

Unpaved roads built over soft, weak subgrade have been used extensively in the Southeast Asian region as temporary site access roads, forest roads and low volume roads. In Singapore, unpaved roads are often preferred in military training areas for better concealment. Vehicular traffic on unpaved roads will cause the base layer and subgrade to deform vertically and laterally. In addition, stones will get pushed into the subgrade and pumping of fines into the base layer will occur under wet conditions, as there is no separation between the base material and weak subgrade. To stabilise unpaved roads, geosynthetics have been successfully used to improve the overall stability and trafficability of these roads. Geosynthetics placed at the interface between the base layer and the subgrade function as a separator as well as a reinforcement to improve the performance of weak subgrade. This paper presented the performance of geosynthetics in the stabilisation of unpaved roads in a laboratory model-tracking test. The effect of anchoring and pretensioning of geosynthetics would be examined. Six laboratory-tracking tests had been carried out for this purpose: one control test, three composite geotextile tests (un-anchored, anchored and with pre-tensioning) and two geogrid tests (un-anchored and anchored). During loading, subgrade settlement of each test was carefully monitored. To evaluate the performance of each stabilisation system, rut and heave resistance of each test were evaluated and compared to the performance of the control test.