Tip Top Ice Cream Void Fill and Re-Level Project

Tip Top had recently decommissioned an industrial freezer located in their Auckland facility, to use as a dry storage area. During the thawing process, they noticed subsidence of the concrete slab on grade. Water run-off around the decommissioned freezer had also washed away soil beneath the facility.

The subsidence grew so severe that a steel support beam in the centre of the warehouse was now suspended from the ceiling rafters above. After self-monitoring for a number of years, they engaged Mainmark to provide a solution. 

The void beneath Tip Top’s decommissioned freezer had to be filled, and they needed to replace the substrate that had washed away during the defrosting of the freezer. The slab would also need to be re-levelled, as near original as possible.

The warehouse plays a crucial role in Tip Top’s operations. Due to this, the client needed half of it to stay operational throughout, while also completing the works as quickly as possible.

The most unique challenge of this project was the construction and design around the freezer itself. Dating from the early 80’s, the freezer’s design required the construction of a slab with a venting structure beneath it, in order to hold products below 0°C. 

This slab consisted of 5 layers — from ground to top level these were as follows:

• 150mm of reinforced concrete,
• 50mm of polystyrene insulation, 
• 100mm of concrete block supports creating vents,
• 50mm of polystyrene insulation, and 
• 100mm of reinforced concrete on top

The large scale of the warehouse and the different site conditions (i.e. severe subsidence as well as open air voids) was also taken into consideration.

The Mainmark team had to come up with a method to address this issue without presenting a hazard to the venting location. They overcame this by using a combination of Teretek resin & JOG for this solution. 

JOG is a computer-controlled, multi-point injection technique. It involves injecting grout with a controlled set time beneath a building’s foundation, which then gently lifts the structure. The lift usually occurs at less than a millimetre per injection. The resulting re-levelling process is uniform and incremental. 

The resin was used to fill open voids visible around the exterior of the structure, while JOG was used to fill the voids 1 metre below ground level. This was done with a series of small 40mm injectors positioned across the centre of the concrete slab.

Mainmark was able to provide both a cost-effective and timely solution for the client. A total lift of 180mm was achieved, across a space measuring 200m².

This was also done in a timely manner, with minimal disruption to day-to-day operations. 50% of the warehouse remained operational throughout the project, which minimised their offsite storage costs.

Additionally, the methodology used kept the re-levelling to within four weeks. This meant Tip Top was fully operational in time for the busiest season of the year — the New Zealand summer.