The Oakey Creek Remediation Project, Lismore Shire, NSW
The slope damage caused by Cyclone Debbie at Oakey Creek Road was massive. Lismore City Council asked us to perform a geotechnical engineering investigation and recommend a resilient and cost-effective course of action. Our solution? Soldier piles.
Cyclone Debbie hit Lismore Shire in April of 2017 and left a trail of devastation in its wake. Lismore city centre was inundated, and severe landslides occurred across the region – the most severe being at Oakey Creek Road, Georgica.
Funding requirements demanded that the Council use contractors for the rehabilitation and slope remediation projects, so they got in touch with us.
We were engaged by Lismore City Council as geotechnical engineering consultants to carry out a detailed geotechnical investigation of the Oakey Creek Road site and to provide a design solution together with detailed construction drawings.
Our primary role was to provide a geotechnical engineering solution, pass it over to contractors to build, and then to manage the project delivery.
The issue we were up against at Oakey Creek was the sheer scale of the slope failure.
There were many options, such as digging out the side of the hill. But we knew that approach would be time consuming and expensive. We wanted a robust solution that was fast, cost-effective and safe.
The weather was also going to provide a challenge. We needed good stretches of dry weather to carry out the remedial works before finalisation of the road, bitumen sealing and installation of the guard rail.
The solution involved a soldier pile retaining wall system. Constructing a soldier pile wall is a detailed and specific process where we install the piles at regular intervals between 1.8m and 3.5m centres. From there, we could support the sub-surface soil between the deep piles and rehabilitate the downslope face.
A soldier pile wall also provides soil resistance. The soil arching transfers the lateral loads into the whole system, which is why it was the perfect approach for this project.
Our geotechnical engineering consultants supervised the site, directing the works every step of the way. We carried out all inspections: bored piling geotechnical supervision and certification, quality assurance, and sign-offs, making sure that the materials encountered conformed to our geotechnical site investigations.
The soldier pile method was cost-effective, and we are confident it will provide a resilient, long-term solution. Soldier piling is a versatile approach, so we were able to save time by making on the spot adjustments during the construction process.