Quinn Piling were awarded the contract to install the piling for City Quays 3, which will be Northern Ireland’s tallest office building. The £50m project will build upon Belfast Harbour’s successful City Quays development, which is currently home to two Grade A offices, a 900-space multi-storey carpark, and a Marriott Hotel.
The fast-growing business hub is already attracting global sector leaders such as Baker McKenzie and ITV. City Quays 3 will continue to offer world class city centre office space in Belfast, providing a significant opportunity for foreign direct investment in Northern Ireland.
Quinn Piling is delighted to have been awarded this contract- a testament to our team’s diligence, expertise and the standard of excellence achieved in our previous work for the City Quays developments.
Piling Scope and Details
The project involved the installation of the deepest CFA piles in Ireland. A total of 468no. 750mm diameter CFA piles up to 34m long have been installed. These include 158no. up to 27m long and 310no. up to 34m long, with loads up to 1,900kN.
The site overlies what was once an old dock that has now been backfilled with very mixed fill material. In order to carry out the piling it was necessary to first prebore at each pile position down to a depth of 5m.
Project Innovation
Due to the site’s proximity to the River Lagan, Quinn Piling had to overcome the notoriously challenging soft estuarine deposits locally known as ‘Belfast sleech’. This locally very soft and organic clay lies beneath the made ground to depths of up to 15m.
This very weak material can cause problems in forming cast insitu CFA piles. To overcome this Quinn Piling used sacrificial steel lining of the CFA piles for the nearby Multi-Storey Car Park and AC Marriott Hotel, however on this site soil stabilisation was the chosen solution.
Soil Mixing
Following a trial mixing and testing programme, Soil Mixing was carried out at each pile position to the full depth of the sleech to increase the strength of the clay. This proved very successful and ensured the pile bore remained stable during the follow-on construction of the CFA piles.
