Fonterra’s transport yard in Te Awamutu, a town in the Waikato district of New Zealand’s North Island, had experienced  subsidence due to unstable soils and voids under the slab. Approximately 100m2 of the 150mm-thick concrete slab had settled by as much as 50mm. The settlement had allowed a build-up of water to form underneath, resulting in the slab moving every time a vehicle drove over it. This indicated that the foundation ground no longer provided the necessary slab support.

Since the transport yard is a busy hub for Fonterra, and crucial to its ability to transport dairy products for sale, it was essential to lift and re-support the slab, making it safe to handle heavy and frequent traffic loads.

Fonterra wanted to remediate the sunken transport yard without the expense of excavation and the yard needed to be fully operational as quickly as possible. In addition, Fonterra wished to avoid the cost of laying new concrete, as the curing time would create delays and the cost of replacing the concrete would have been prohibitive.

Mainmark was appointed to fill the voids and lift the slab back towards level in a uniform and controlled manner, with minimal impact to the site’s core daily functions. Using its proprietary Teretek® engineered resin injection solution, Mainmark filled the voids, lifted the slab, and stitched sections of the slab back together. The project was successfully completed in a single day without disruption to Fonterra Te Awamutu’s operations.

With up to 500 vehicle movements per day, Mainmark was required to raise and re-level the slab within the transport yard to as near as level, efficiently and with no impact to traffic flow.

Mainmark also had to address the significant cracks and gaps in the 100m2 surface of the slab, to deliver a safe and level area suitable for heavy vehicles.

Teretek® was specified because it could improve the foundation ground while raising and re-levelling the slab in a single application. This solution resulted in a far more cost-effective alternative to traditional underpinning processes, which can be expensive

and disruptive. The Teretek® resin is injected intothe ground at specified points. When the expanding polyurethane mix enters the ground, the components mix together and expand, filling the voids, strengthening the ground, and also re-levelling the slab.

Mainmark completed the project in a single day, avoiding the time and cost needed to excavate or pour new concrete. The transport yard’s slab was safe to drive on a few hours after the application, ready to take the load of heavy trucks.