Te Awa Cycleway Stabilisation, Hamilton – Platipus Anchors

The Te Awa Cycleway runs adjacent to the Waikato River, travelling 65km from Ngaruawahia to Lake Karapiro. It comprises mixed surfaces of concrete and wooden paths over streams, past historic sites, waterfalls, cafés, and picnic spots.

Between Hamilton and Tamahere, the Te Awa Cycleway cuts through steep embankments, hillsides, and gullies at the river’s edge. These slopes required stabilisation, adding support to the upper and lower slopes before the path could be constructed. With the path placed close to the water’s edge, there was little room for construction of conventional reinforced walls. Hamilton City Council required a solution that would be quick to construct, stable during construction and safe for recreational use.

DESIGN

Soil anchors were considered, but they require placement, grouting and time to set, meaning they are slow to become operational at full strength. For this reason, percussion driven Platipus Earth Anchors were the obvious solution. Rapidly installed and immediately operational, Platipus anchors can be driven in, locked and tensioned, then tested during installation, effectively loading them to their design capacity.

Timber retaining walls with piled foundations were designed to reinforce the toe of some steep slopes, both above and below the path area, creating an area of level ground where the pathway could be positioned. Platipus Civil Anchors could then be driven through the poles into the earth, giving horizontal support. DuraFlow drainage composite would be placed behind the walls to help with water flow.

Unsure whether B4 or B6 anchors would be required, Earthtech Consulting gathered geotechnical information regarding the soil structure within the slopes. On site testing was conducted, deducing that liquefication could become an issue whilst driving the anchors into the riverbank silt. To limit this, the larger B6 anchors were to be used, driven in 4-5m and loaded to the relevant design load required for each section. These would create sufficient tensile strength to stabilise the slopes, but it was important that the anchors could be installed, tensioned, and tested in real time.

Additional ARGS anchors with DuraMat and T-RECS turf matting were also used to stabilise the upper slopes and some access roads to the site.

INSTALLATION

Cirtex supplied all Platipus installation tools and provided contractor training on site, enabling Keir Landscaping to install and test the Platipus anchors themselves. Working within a stream, with little room and a high water-table, Keir Landscaping used excavators to cut platforms, install reinforced walls and drive the anchors into the slopes. Challenging construction conditions that would otherwise have taken much longer were made simpler and faster by using Platipus anchors.

The Geotechnical Investigation provided estimated depths of competent material. By conducting insitu testing during the installation of the Platipus Anchors, the depths could be adjusted to ensure the correct design anchor loadings were achieved. By penetrating and locking into competent material, the Platipus Anchors reduce the need for additional retaining.

Cirtex, Grey Matter Consulting and Keir Landscaping worked together on site, giving Hamilton City Council assurance that the Platipus B6 Anchors were suitable for the task. With the challenging terrain, tight budget and time constraints, Platipus Anchors were a simple, rapid solution. Hamilton City Council saved money and time, and the Te Awa Cycleway is now a recreational journey that families will enjoy for generations.

The Platipus Anchors provided the following benefits to the project:

• Immediately fit for purpose, proof testing and depth adjustment can be carried out during installation.
• Able to be installed and tested by local crews with Cirtex on-site training.
• Capable of stabilising steep slopes without the need for additional retaining.