This week contractors began the lengthy process of jet grouting the quakedamaged building’s foundations. They are using three grout machines that have been imported from Germany for the work, during which more than 1000 large concrete piles will be injected eight metres into the ground.
In the February 2011 earthquake the land beneath and around the Town Hall was severely damaged. Although the building itself fared relatively well, significant strengthening of its foundations is needed. Jet grouting has been identified as the most effective repair solution to address the land issues underneath the building.
‘‘Grout and water is injected into the ground at high velocity to create columns of soilcrete, which is soil cemented with grout. The columns will overlap and interlock to create an earthquake resistant underground wall of columns that will protect the building from soil movements,’’ said Project Manager Paul Youngman.
A total of 27,000 cubic metres of jet-grout concrete – which would fill 270 average family swimming pools, 37,500 bath tubs or 200 buses – will be used during the process.
A thick concrete slab will be laid over the concrete columns once the jet-grout work is complete, which will help to bring the Town Hall up to 100 per cent of New Building Standard.
Contractors have spent five months preparing the site for the jet-grouting work, which is expected to be completed in June next year. It is the first stage in the $127.5 million repair of the Town Hall.
Christchurch City Council anchor projects unit manager Liam Nolan said the restoration work would ensure the Town Hall could continue to be enjoyed by Christchurch residents for the next 50 years and beyond.
‘‘The Town Hall is one of the city’s most treasured civic and heritage buildings and this restoration work will ensure it is better and stronger than it was pre-earthquake. Starting on the Town Hall foundations marks the culmination of four years of work. This has included engineering assessments, going through a tender process and appointing a contractor to undertake the restoration work,’’ Nolan said.
‘‘By the time we’ve finished work on foundations, the ground underneath the building will be significantly stabilised, ensuring we can get on with the rest of the work needed to restore this building to a world-class facility that can be used for many years to come.’’ .
The restoration of the Town Hall, which also includes a significant upgrade and refurbishment of the facility, is due to be completed in 2018.
- Lois Cairns
- The Press