Temporary Retaining Structure – Platipus® Earth Anchors

To future-proof Whangarei’s water supply, a new Water Treatment plant has been constructed which will increase the water supply capacity from the existing 15,000m3/day to 22,000m3/day. As part of the construction, a large underground tank was to be buried within close proximity to one of the new buildings. The problem was that the excavation required for this tank could undermine the building footing at one corner.

Design

To maintain the structural integrity of a critical building foundation the engineer specified a temporary retaining wall consisting of UC posts and 150mm diameter timber poles as lagging with two rows of Platipus Anchors driven between the posts to a minimum depth of 6m. A 200mm diameter timber pole was used as a temporary waler to span between the UC posts with a 100x100x20mm square load plate. The upper row required B8 size Anchors with a proof load of 30kN and the lower row required the B10 size anchor with a proof load of 120kN. The soil onsite was classified as a firm silty clay with a layer of soft silty clay underneath.

Installation

On the first day of installation, a Cirtex technical support representative met with the contractor crew to provide training. The contractor used a 5-ton excavator with a hydraulic breaker to drive in the Anchors to the required depth. Each Anchor was tested to the designed load specified by the engineer using specialist hire equipment from Cirtex.

The Platipus B10 Earth Anchors used provided the following benefits to the project:

• Provide a safe working environment for construction crew responsible for installing the tank
• Maintain the structural integrity of a critical building
• A solution that could be easily installed with onsite installation training from a Cirtex technical support representative
• Ability to quantify the holding capacity of each anchor immediately after installation