The idea of using PU resin for ground strengthening was originally introduced by a Scandinavian company to help address ground movement and subsidence that can occur each year due to Europe’s extreme weather cycle, which freezes then thaws the ground.
The science behind polyurethane (PU) resin as a ground engineering solution is a homogenous mixture in two parts. When the homogenous resin is injected into the soil, it instantly reacts, forming a rapidly expanding foam that seeps into any ground voids and fissures, filling gaps and creating a bonding effect with the soil particles.
The pressure from the expansion of the resin compacts the surrounding soil to significantly strengthen the ground, increasing the bearing resistance of the soil without increasing the weight or overburdening the soil. When the solution is injected beneath a structure, the expansion pressure lifts the structure, remediating differential settlement without the need to excavate.
Mainmark’s founder, Philip Mack, introduced polyurethane resin as a ground strengthening solution to Australia after researching ground engineering innovations following the 1989 Newcastle earthquakes. After remediating a number of earthquake affected buildings, Philip saw an opportunity to use the solution to re-level sunken slabs. He subsequently travelled to Scandinavia to investigate bringing this technology to Australia.
However, at the time, there was scepticism about the effective use of resin as a ground strengthening solution due to the lack of scientific evidence. The idea that there was a quick, cost-effective and non-invasive way to lift a building’s foundations without the need for expensive concrete underpinning was hard for the industry to conceptualise, and there were no design tools to assist engineers.
It wasn’t until Professor Olivier Buzzi, chief investigator with the ARC Centre of Excellence for Geotechnical Science Engineering and lecturer at the University of Newcastle undertook an investigation in 2007, exploring the structure and properties of expanding PU in the context of foundation remedial works, that Australian engineers started to take notice.
Professor Buzzi wrote a research paper which was co-authored by Mark Yasumasa Sasaki, a Mainmark long-term employee, titled “Structure and properties of expanding polyurethane foam in the context of foundation remediation in expansive soil“, which concluded that the injection of expansive polyurethane resin was an effective method for remediating differential settlement.
The University of Newcastle funded research also concluded that polyurethane expanding resins were suitable to use underneath building foundations and that the expanding resin didn’t impede the reactivity of clay soils. Professor Buzzi’s research was a breakthrough in gaining wider acceptance of polyurethane resin as a ground strengthening solution within the wider engineering community. Until this point, the only scientific research available was based on European soils that didn’t consider Australian soil types; specifically reactive clay.
Yet while this research was a major milestone, Mainmark has continued to push the boundaries by independently supporting further research. The company had a theory about a new technique using polyurethane resin to remediate seismic liquefaction. Following the 2010 and 2011 earthquakes in the Canterbury region of New Zealand, more than 15,000 homes were demolished due to the effects of liquefaction. This initiated a series of resin injection trials in a designated zone severely affected by liquefaction known as the Christchurch Red Zone.