Project - Underpinning

This week at AEGIS, I had the opportunity to supervise a non-invasive chemical underpinning project undertaken by Mainmark at a mixed-use property in Wollongong, comprising retail tenancies at ground level with residential accommodation above.

The property was experiencing structural cracking within the external brick walls resulting from differential foundation settlement. To address the issue, an innovative ground improvement solution, which is environmentally inert and water-resistant, was adopted using expanding polyurethane resin, formed through the reaction of isocyanate-based components, injected at depths ranging from approximately 1.0 m to 2.0 m beneath the existing foundations.

What makes this technique particularly impressive is its dual ability to simultaneously stabilise/strengthen the sub-ground soil and re-level the building foundations above without the extensive excavation typically associated with traditional underpinning methods. By completely avoiding excavation, the solution significantly reduced disruption to occupants and businesses, eliminated the need for spoil removal, and minimised construction waste generation, demonstrating a practical and sustainable engineering approach.

A key aspect of the works was the real-time monitoring and verification of structural response. The lifting of the wall footing and closure of cracks were continuously monitored using NIVCOMP precision levelling equipment internally and dumpy level surveys externally around the injection locations. Witnessing the gradual closure of visible cracks as the foundation responded to the controlled injections was a fascinating example of engineering theory being translated into measurable on-site outcomes.

Projects like this highlight the value of innovation, sustainability, risk management, and evidence-based decision-making in engineering practice. Through my role at AEGIS, I continue to gain exposure to a diverse range of structural and geotechnical remediation techniques that expand my understanding of how complex asset performance issues can be addressed efficiently and with minimal environmental impact.

A sincere thank you to the Mainmark team (especially Grant Wells) for their professionalism and for sharing their expertise throughout the works. Experiences like these reinforce that continuous learning and collaboration across engineering disciplines are essential for professional growth and delivering better outcomes for our communities and the built environment.