Project Overview
The Gatton Clifton Road, located 20 km from Gatton and running alongside Ma Ma Creek, has a long history of slope instability due to its deeply weathered geological profile. Severe rainfall events between December 2010 and January 2011 caused major damage, closing the road to a single lane for more than two years while authorities sought a long-term stabilisation solution.
The original tender called for a 200m-long soldier pile wall using 900mm bored piles, but the unstable slope and support requirements for heavy piling rigs made this design prohibitively expensive, consuming nearly $1 million in temporary works alone. PCA offered an alternative: a micropile A-Frame slope stabilisation system, previously proven in local council projects but never before approved as a permanent solution for a state road authority in Australia.
Challenges
- Deeply weathered geology prone to landslip
- Previous slope stabilisation attempts (buried gabion structures) complicating design
- Original bored pile design requiring extensive, costly temporary works
- Safety and stability concerns supporting large piling rigs on unstable terrain
- Proposed six-week full road closure for bored pile installation
- No existing Australian or State design standards for permanent A-Frame micropile systems
Innovative Solution
PCA, in collaboration with TMR’s Geotechnical Branch, designed and delivered a 200m-long micropile A-Frame structure, divided into six distinct design sections. Key solution highlights included:
- Inclinometer monitoring installed to track long-term slope performance
- Ability to drill through buried gabion structures without removal, saving time and cost
- Use of zero-swing excavators enabled works to proceed under single-lane traffic control rather than full road closure
- Structure proven to perform within design parameters after multiple significant rainfall events
- Project established as the first permanent A-Frame micropile system adopted by a Queensland state authority
Outcome
- Road reopened with minimal disruption to the community
- Significant cost and time savings compared to the bored pile option
- Permanent slope stabilisation achieved with lower environmental and logistical impact
- Recognition through a TMR Innovation Award and a Civil Contractors Federation National Award
- Positive client endorsement via reference letter from the Superintendent praising PCA’s solution