Ground strengthened and building re-levelled at large shopping centre

Mainmark’s Liquefaction Mitigation offering is the only solution of its kind and can be applied retrospectively beneath existing buildings or structures. The ground beneath the Northwood Supa Centa was treated via more than 3,000 injection points to a depth of between 4m to 8m below ground level, and across the building’s footprint.

Extensive pre and post installation CPT (cone penetrometer testing) was undertaken to ensure the solution provided the designed soil improvement and resistance to liquefaction, thereby satisfying section 112 of the Building Act 2004.

Once the ground improvement was completed, JOG Computer-Controlled Grout injection was used to correct the building’s settlement and re-level the building. This was a precise process with corrections applied beneath all load bearing foundation elements, including the internal party walls for three adjoining structures.

Mainmark also developed bespoke technology and equipment for the Northwood Supa Centa project to capture and assess the large amounts of data for each of the 3,000 plus injection locations.

From an operational perspective, the Northwood Supa Centa project was a significant undertaking for Mainmark. Its project team worked tirelessly on site effectively 24 hours a day, six days per week over a three-month project period while the centre continued to operate uninterrupted thanks to a clean and non-invasive remediation process. The internal works were completed outside of trading hours throughout the night, while external works were executed during the day, without the need for retail tenants to close their stores or be impacted by mess or noise. Alternative methods to address the site and building issues would have turned the centre into a dirty and dangerous construction zone requiring businesses to vacate the premises for several months.

The shopping centre remediation works have since achieved a 100% NBS result, which will help ensure that it is protected against the effects of future earthquakes.