Work is currently underway, on the seafront near the site of Brighton’s historic West Pier, to build the Brighton i360,a visitor attraction which will be the world‘s first vertical cable car and is designed by the London Eye architects, Marks Barfield.
Once completed, the Brighton i360’s tower will be 162 metres high and will carry visitors in a glass observation pod that will glide up slowly to 138 metres, making it Britain‘s highest observation tower outside London –
taller even than the London Eye.
Visitors will have 360 degree panoramic views giving a new perspective of Brighton and Hove with its Regency squares, Grade II listed Victorian pier, seafront and Royal Pavilion. On a clear day, they will be able to see for more
than 40 km: across the Seven Sisters and Beachy Head to Bexhill-on-Sea in the east, Chichester in the west, over the South Downs National Park to the north and far out into the English Channel to the south.
The key contractors involved in the construction of the i360 are the Dutch company Hollandia, who are fabricating and will erect the steel tower, the French company Poma, who are manufacturing the visitors’ pod and local firm J.T. Mackley & Co Ltd who are carrying out the civil engineering works on site. Mackley, based in Small Dole, West Sussex and founded in 1927, have extensive experience in major infrastructure projects and have made a speciality of delivering projects at coastal locations.
The first task that faced Mackley as they started the project was to divert a large sewer and power cables that ran through the site. Then the site had to be piled, a task subcontracted to Simplex Westpile who installed 43 bearing
piles and 252 secant wall piles.
The bearing piles are external to the tower and have been constructed to support a single storey reinforced concrete building. This building will house the ticket office, a large beachside cafe/brasserie, an exhibition space, a shop, a children‘s soft play area and a dedicated hospitality suite with rooms available for private events, conferences and weddings.
The secant wall piles were installed to provide a retaining wall to allow the excavation of a basement to house the main foundation for the tower. The foundation is a 24 m x 24 m x 3 m deep, reinforced concrete base with a
ring of bolts cast into the concrete to support the main tower. This base is not supported on any piles, rather it is supported directly on the chalk. The piles only serve as a retaining wall; the load from the tower is not in any way
transferred into the piles. The base was poured in two layers, the first approximately 2 m deep and the second 1 m deep. The first pour, of approximately 1,200 m3 concrete was carried out on a Saturday at the end of May 2015. Due to the high volume of concrete to be placed, Mackley chose to use two local ready mixed concrete suppliers; Hanson, who supplied from their plant at Shoreham Port, Portslade, and Dudman, who supplied from Southwick.
The concrete mix supplied by both companies was a C28/35 mix with a minimum cement content of 320 kg/m3, water cement ratio of 0.55 and consistence class of S3. There was some concern that the mass of concrete would generate excessive heat and would be susceptible to thermal cracking. To minimise this risk, a blended cement (50 % Portland cement and 50 % Ground Granular Blastfurnace Slag) was chosen and a controlled delivery rate of between 100 and 120 m3 per hour was planned. Pumps for the first base pour were hired from Camfaud Concrete Pumps Ltd. Four Putzmeister truck-mounted pumps were supplied on the day; three working and one on standby:
1 x M 47-5, 1 x M 38-5 and 2 x M 36-4 boom pumps.
The standby pump operator acted as the relief operator, allowing each driver to get regular breaks in turn during the day. All of the pumps supplied were high volume models with a theoretical output of up to 160 m3/h. Though this output was not required, the large cylinder, slow stroking design of the pumps ensured that there was minimal movement in the boom, making for an easier day for the hoseman. In keeping with the i360 project’s ethos of sustainability, the pumps supplied were all mounted on the very latest, low emissions, Mercedes Benz, Euro 6 truck chassis.
In addition, the M 38-5 pump supplied uses biodegradable hydraulic oil to further enhance its green credentials. The placing boom of each pump was equipped with a pneumatic, end hose shut-off valve to prevent
concrete from falling from the boom while being repositioned. This prevented material spilling onto finished concrete but, more importantly, created a safer working environment for the concreting gang.
The pumps arrived on site at 05.00 and were set up in time for the first load of concrete which arrived on site promptly at 06.00. With Mackley’s logistics team coordinating the traffic, Hanson and Dudman achieved the desired delivery rate and the pour was completed in a fraction over 12 hours. Once the pour had been completed, the pumps were cleaned out, derigged and left site to return to their depots. The consensus, from all those
taking part, was that the pour had been a great success, going exactly to the plan that had been developed over the previous months. And thousands of locals, day trippers and holidaymakers strolling along the seafront that day
seemed intrigued by the activity with many stopping to watch for a while and take photographs. In addition, hundreds more were able to watch online via the i360 webcam and participated via social media, excited as the project
completed this major milestone.