A new addition to the bridge foundation designer’s toolkit Monday, 08 July 2019

SPONSORED CONTENT: A drive through the countryside in many regional centres quickly reveals the ageing bridge assets coming to the end of their design life across the country. In addition to the many old and tired bridges in need of replacement, the demands from the modern transport industry are putting pressure on many older bridge assets to be replaced or upgraded to open up the regions for greater economic prosperity through a more efficient transport network.

Many regional bridges are small single, double or triple span structures in rural locations vital to the local communities. Access to the bridges is often along rural roads and other small load restricted structures that need to be considered during the construction of the new bridge. These restrictions can be at odds with the equipment required to install traditional piled foundations adding significant temporary works costs for the operation of large diameter bored or driven piling rigs.

The emergence of micropiles as an alternative to traditional piling methods in regional bridge replacement projects in South East Queensland and Northern New South Wales has produced significant cost, environmental and social benefits to Councils and their communities. No longer do Councils need to pay for expensive piling platforms and temporary works since the micropile construction process involves small and flexible machinery more suitable for regional and rural construction.

A recent project for Byron Shire Council in Northern NSW involved the replacement of five old timber bridges with new “Baily bridges” supported on piled foundations. Access to these bridges required construction equipment to traverse several load restricted structures and winding roads limiting access of traditional large diameter bored or driven piling rigs.

The alternative design provided by PCA Ground Engineering included an array of micropiles in lieu of the conforming large diameter bored piles. The equipment used to install the micropiles ranged from a small 8 tonne drill rig to a 24 tonne excavator mounted rig depending on the access restraints.

The resulting benefits to the project included;

  • Reduced traffic on the local road network. There was no requirement for concrete trucks for the piles or for trucks to remove excavated material from the piling process.
  • Significantly less environmental impact on the creeks and rivers adjacent to the bridge sites due to the removal of temporary piling platforms or the need to improve local access tracks.
  • Zero risk of variations from latent conditions that would normally impact on driven or bored piles. Micropiles can be drilled an installed through most naturally occurring materials including boulders and collapsing soils.

Anyone interested in finding out more about the design or use of micropiles in this or other similar projects are invited to attend the upcoming 14th International Workshop for Micropiles to be held on Queensland’s Gold Coast from August 21st to August 23rd 2019.

Information and registration details can be found by following the link on the PCA Ground Engineering web site, www.pcagroundengineering.com.au.