Summary
Back in 2015, the directors of a heritage apartment building in Elwood, Victoria were faced with a challenge: many cracks had developed gradually over the building’s life, which were aesthetically unappealing and in need of costly, cyclic repair.
“Cracks have long been the talking point of the building and many approaches had been taken to help solve the issue without lasting success,” said Janice, one of the directors.
Cracks in a building can be a warning sign for serious and ongoing structural damage. The Elwood apartments were built on reclaimed land with more than two metres of silty clays overlaying the area’s natural clay. Tidal movement of water in the nearby canal and large adjacent tree roots had caused the soil to shift and the building’s foundation to lose its strength. As a result, the building sank unevenly causing cracks to appear in the walls.
Objectives
The Mainmark team addressed the core issue by compacting the foundation ground and completely re-supporting and re-levelling the building. This approach minimised disruption to residents’ daily lives and preserved the interiors.
“Conventional methods of re-levelling had posed risks of major damage to interiors, with some introducing differential settlement of walls across the building. It was essential to find a solution that would minimise impact on interior spaces.
“Retaining the floors was especially important to me, because in my apartment they include terrazzo that was hand-laid by my artisan father. I wanted to preserve this active legacy of his artistry,” said Janice.
Technology used
Mainmark used a unique ground engineering technique known as PowerPiles which are polymer pillars that can be installed under existing buildings to easily retro-improve foundations.
Installed PowerPiles are geotextile shells filled with an expanded resin that compresses the soil to strengthen the building’s foundation. The process involves driving pre-fabricated tubes into the ground through small 38 mm Ø holes. The tubes are then filled with expanding structural resin and the shrink wrapped shells then expand to up to 340mm Ø, compacting surround subsoils.
Using a structured and controlled process, the Elwood building was entirely re-supported by 48 PowerPiles. Additional resin Deep-Injection was used between the PowerPiles for additional and continuous support.
The process did not require excavation or large holes to be drilled, minimising mess.
Outcomes
Three self-contained Mainmark operations units re-supported all internal and external walls onto the natural clays and successfully compacted the soil beneath the building’s footings in just five days.
“Mainmark provided a solution that addressed the problem and allowed us to retain our love of the place. It has assured the viability of our floors and returned our walls to level.
“We are very happy and relieved this work has been done. The process was systematic and controlled, and it was a pleasure dealing with the team.
“As an owner within a heritage apartment block, I cannot stress enough the new lease of life Mainmark has allowed our building to have. It can continue to stand proudly as an original icon in its glorious Elwood setting,” said Janice
