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Basement construction technique at St George's Hospital - A Canterbury first

March 2014

A pioneering, low-vibration ground strengthening technique being used at St George’s Hospital will minimise the impact on patients and neighbours during the initial construction stages of the $122 million redevelopment. 

Stage One involves construction of a large basement on the site of St George’s iconic 1928 heritage building which was demolished in 2012 – above which a new cancer care treatment centre, four-storey atrium, reception area, staff café and chapel will be built.  

It’s the first time in the Canterbury rebuild  that the method has been used for a large basement and the work will involve drilling deep soil mixing (DSM) columns to create a secant pile wall.  

DSM is an advanced method of strengthening liquefiable ground conditions. A variety of binders are injected and mixed with site soils to produce uniform, high strength columns that stabilise the ground for construction. 

Hiway GeoTechnical completed 18 trial columns in November 2013 to help fine-tune the methodology and planned layout of the wider ground improvement programme. The project involves drilling an additional 726 DSM columns throughout the St George’s Hospital site.  

Canterbury Manager for Hiway GeoTechnical, Joel McLean, says there will be minimal disruption to patients, staff and the community.  

“The process causes extremely low vibration and the noise can be likened to that of a standard digger being operated, which is beneficial given the nature of the environment that we will be operating in. 

“The permanent secant pile wall is a low vibration alternative to the more common high vibration temporary sheet pile wall traditionally used for basement construction.” 

St George’s Hospital suffered damage during the earthquakes of 2010 and 2011. A three-stage redevelopment is planned from now until 2019. Most of the project will be covered by St George’s insurance earthquake pay out, accumulated reserves and future surpluses until the buildings are completed. 

Construction of Stage One will fully commence in March 2014 and is expected to be complete by September 2015. 

Stage Two is a new four-storey building housing radiology services, operating theatres, instrument sterilising services, and intensive care and high dependency units. It is expected to be complete in late 2016. 

Stage Three includes more operating theatre suites and education rooms. Construction is expected to be complete in early 2019. 

St George’s Hospital Chief Executive Greg Brooks says the community will be kept well-informed throughout the redevelopment. 

“The ground improvement work is a great step forward in the construction of our new buildings and facilities. We will liaise directly with the community to ensure residents are regularly updated – this includes holding open days so people can see first hand what is happening on site.” 

The first public open day will be held on Saturday 29 March 2014, between 10am and 1pm. 

St George’s Hospital will remain fully functional throughout the redevelopment, with some services being relocated between buildings as work is completed. 

“The safety of patients, visitors and staff is our number one objective,” says Greg. “Throughout these developments we will maintain a safe environment for everyone working at or visiting the hospital.”


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