Our Lady of Consolation Aged Care Services is building an independent-living apartment building in Toongabbie, Sydney. Of the building’s seven storeys, five are independent living residences that cater to local late-age women who live alone and cannot support themselves financially. The project also includes commercial premises on the ground floor. The project is being built by Total Construction and is due to be finished in July 2019.
The project suffers from a problem typical to Sydney multi-storey constructions: the neighbours bordering the building do not want traditional ‘anchors’ used to shore the basement walls, driving into their property.
Anchoring means cables are driven sideways through the walls of the excavation and into the ground beyond. Once anchored they ‘pull’ back on the basement wall. Total Construction needed a safe alternative to anchoring, that allowed work to progress efficiently and safely.
Construction Project Manager for Total Construction, Damen Hills, says with anchoring removed as an option in the two-level parking basement, the company first looked at an internal shoring solution using structural steel.
With internal shoring, the traditional approach would be to install steel waler beams against the inside face of the basement wall and use props to ‘push’ the walers against the wall, preventing it from moving.
But the Total Construction project team did not favour this approach.
“The structural steel method would use two main cross props, each dissecting the 35 metre by 35 metre pit, chopping it into quadrants,” says Hills.
Their excavation teams would be hampered by the cross beams, slowing the removal of earth; and Total was reluctant to use a large amount of steel that would later be dismantled and discarded.
Hills says he and his colleagues wanted a better solution and they saw a story on LinkedIn about Coates Hire’s fleet of Hydraulic Struts.
“We called Darren Browne at Coates Hire, and we moved very quickly from that phone call,” says Hills.
Working in consultation with the structural engineers for the project, Van Der Meer Consulting Engineers, Coates Hire’s team of temporary works designers developed a more effective method of internally supporting the basement. The key feature of the design was to use reinforced concrete corbels that tied into the concrete retaining wall, and stood out from the top of the excavation. The hydraulic struts were connected to the corbels, above the height of the future basement slabs. It allowed Total Constructions to perform their excavation and construction of the basement without any of the shoring system getting in their way.
Hills says the Hydraulic Strut system is re-usable and modular, so it is adaptable to the needs of the site. And the Coates Hire engineers designed it and ran-it-up in their own yard before it arrived at the site so there was no delays at installation.
“It was installed in four days, and removed in three days at the end of the contract. It was very safe and very impressive.”
Temporary Works Engineer from Coates Hire’s Engineering and Technical Services Team, Darren Browne, says the various criteria of the project included shoring it safely without using structural steel and anchors, and creating additional space for the earth works.
Damen Hills says the Coates Hire team was a “one-stop shop”, complete with engineers who worked with the other project engineers to create solutions.
“The system was not cheaper than structural steel but it saved us money because we spent 30 per cent less time on the basement than we otherwise would have,” says Hills. “Saving time is important in the construction business, and Coates Hire helped us do that.”