Projects

Background

Australia annually spends approximately $16 billion on construction and maintenance of its 911,000 km and fast growing road network (Australian Local Government Association, 2014). Roads are constructed on natural soil (subgrade) providing adequate cover (pavement structure) to safeguard subgrade against repetitive vehicular load. Where the subgrade is weak (for example, California Bearing Ratio (CBR) less than 8%), greater pavement thickness is required. The pavement structure comprises several layers of unbound (granular) and bound (asphalt, concrete, cemented granular) materials. In general, pavements consume a large amount of crushed or natural aggregates extracted from a stock of depleting natural resources. Cost effective, efficient and environmental friendly roads can be constructed by stabilising subgrade with geogrids (Figure 1a) to reduce the thickness of pavement required over the subgrades. Further, geogrids may improve drainage of subgrade, reduce subgrade expansion (swelling) and reduce the loss of pavement thickness by gravel particle penetration into the subgrade.

However, the use of geogrid in granular flexible pavements is not widely used by the Australian road authorities primarily because of lack of (1) bottom-up (i.e., based on fundamental understanding) design method dealing with the usage of geogrids in pavements, (2) laboratory methods to determine the modulus and performance equation (rutting equation) for geogrid reinforced granular layer,  and (3) material specifications to select geogrids from a number of different products available in the market. 

Project Objectives

1. To investigate and understand the stabilisation mechanism of geogrid/geocomposite in subgrade/granular pavement stabilisation

2. To identify the optimum location of geogrid/geocompositein reinforced granular pavements

3. To develop andvalidate the numerical models for predicting the performance of geogrid-reinforced pavements subjected real-world traffic loading

4. To develop a rational design approach forpavements with geogrid stabilised subgrade/granular layer to incorporate into the existingpavement design methods in Australia

5. To develop laboratory test procedure and material specifications to identify a geogrid/geocomposite product as subgrade/granular layer enhancement

6. To develop a methodology to calculate the cost-benefit ratio when using geogrid/geocomposite in granular pavements