Cementation Skanska has played a vital role in the re-development of Buchanan Wharf in Glasgow, a large development on the banks of the river Clyde facing the International Financial Services District.
Drum Property group secured a multi-million pound deal to develop a new headquarters for Barclays Bank, which will give life to grade-A office space for approximately 2500 people – almost doubling Barclay’s current workforce in Scotland. Cementation Skanska was brought in to provide piling and ground engineering solutions at the site, known as Building 1 and 2.
Having demonstrated our capabilities on the first two sites, the team was contracted to work on Building 3, a new university student campus, and Building 5 – a 240 residential apartment block for sale/rent, commissioned by Legal & General in this revitalised quarter of Glasgow.
The challenge
The team faced three key challenges:
- The geological complexity of the site: significant variations in rock levels and prevailing ground conditions, including a 2m deep layer of clay below platform level causing flooding issues at Buildings 1 and 2, called for a highly innovative approach and specialised piling expertise
- Timescale: with a commitment to opening the Barclays HQ in 2023, main contractor McLoughlin & Harvey needed to appoint a specialist ground engineering contractor with the right expertise and equipment that could mobilise in line with project milestones
- City centre location: bringing in large piling rigs, housing specialist equipment and completing works in a tight city centre location brought its own logistical challenges
The solution
On Buildings 1 and 2, the depth of the underlying bedrock, at 35m – 40m below ground level, meant that the installation of piles using standard temporary casing was not an option. We decided the most effective piling solution for the project was large diameter rotary bored piles using bentonite support fluid. This is a piling technique that we have successfully used over the years throughout Glasgow city centre.
We developed a solution that involved sinking 35m to 40m deep bentonite piles to support the main structures. This technique uses bentonite as a support fluid for each pile bore. Prior to concreting we removed the old (dirty) bentonite and replaced it with clean. This activity all took place from the Bentonite farm we installed on site.
This technique requires the right combination of skills and equipment. In order to complete the works to the required timescale we were able to rapidly mobile four piling rigs and bring them to the tight city centre location. In total we installed 173 piles, ranging in diameter from 900mm to 1500mm, together with eight anchor piles – four at 900mm and four at 1050mm.
The success of our work on Buildings 1 and 2 led to our appointment by Graham Construction on Building 3, which had a similar geology and required a similar solution. In total we installed 71 piles ranging from 1050mm to 1500mm diameter and six associated anchors at 1500mm diameter.
On Building 5, we were brought in by Graham Construction to develop an alternative piling solution to the previously considered option. We successfully tested an alternative solution using soil displacement piles (SDP) for the lighter outer sections of the building. This method halved the depth of the piles to 12m, with a consequential cost saving and reduction in environmental impact by reducing the need for offsite soil disposal. We used continuous flight auger (CFA) piles for the core structure, which required drilling through the bedrock to 26m below the surface.
In total we installed 143 SDP piles at 510mm diameter and 78 CFA piles at 900mm diameter, together with 18 tower crane piles at 900mm diameter.
The outcome
Despite the significant and varying conditions encountered across the sites, we were able to work closely with our customers to develop bespoke solutions that met the specific challenges of each location. Despite working in a tight, busy, city centre location we maintained an exemplary safety record with no lost time accidents reported. All piling work was completed on time, on budget and to the right quality standards. Our technical expertise combined with our collaborative approach led to the development of successful and lasting working relationships.
