Combigrid Pavement Construction at QLD’s Cunningham Highway

Project snapshot

The Warrill View section of Queensland’s Cunningham Highway carries some 5000 vehicles per day. As a major freight corridor between Sydney and Brisbane, 16% of its traffic is heavy vehicles.

This section of the highway was extensively damaged during the major flooding activity in 2011. To improve safety and flood immunity, a 3km section of the Cunningham Highway through Warrill View has been upgraded with a combination of new road pavement and repairs to the existing pavement to provide better road infrastructure, ensuring this major route remains open in all weather conditions.

The challenges

To improve the bearing capacity of the soft subgrade (existing <2% CBR) and therefore reduce the thickness of the required pavement, a geocomposite reinforcement solution was suggested by the designer.

The geocomposite was a geogrid to provide reinforcement and a nonwoven geotextile to provide filtration and separation. The geocomposite had to comply with the requirements of a Type 2 reinforcement geosynthetic in accordance to QLD TMR specification for subgrade reinforcement: MRTS58 (2015).

Our solution

After reviewing some available products, Combigrid® geocomposite was selected to be used in this project. Combigrid® was approved for use by the Queensland Department of Transport and Main Roads (TMR).

Combigrid® geocomposite is made of a biaxial laid and welded Secugrid® geogrid for reinforcement combined with an integral nonwoven geotextile (integrated between geogrid bars) for separation and filtration. It offers higher radial stiffness than competing products, higher installation damage resistance, and better performance based on available full-scale trials.

Combigrid® also has a wealth of technical support available combined with successful application and experience on many previous TMR projects.

More than 50,000m2 of Combigrid® 40/40 was successfully used in the project. Combigrid® has been approved by Qld TMR to meet MRTS58 requirements and has been successfully used in many large infrastructure projects including the Brisbane Airport New Parallel Runway access roads, Moreton Bay Rail Link platforms, Bruce Highway upgrade - Cooroy to Curra, D’Aguilar Highway upgrade and Gateway Upgrade North Project, to mention a few. Construction of this project was completed in mid 2017.