1 Broadgate, London
The Layers of London
More than 65,000 cubic metres of soil was excavated to form the basement of 1 Broadgate. By removing so much soil, we are revealing London clay which may not have seen the light of day for millions of years, giving us a window into the past. To see how this London clay was formed, we need to go back more than 50 million years –
- 56 million years ago, where London is situated now, the area would have been a sub-tropical forest on the edge of a sea. Changes in the sea level during this period resulted in much of the land being submerged under water, depositing London clay up to depths of around 150 metres.
- By 25 million years ago, the sea levels had dropped, and long periods of erosion worked away layers of clay before the Anglican Ice Age brought in huge layers of ice 425,000 years ago.
- The first iteration of London itself, Londinium, was then formed by the Romans in 40AD, becoming the capital of Roman Britain. The city was bounded by a wall with seven main gates. The 1 Broadgate site would have been situated just outside of Bishopsgate, on the banks of the lost river Walbrook.
- In medieval times (1247) the site would have been situated next to the priory and hospital of St Mary of Bethlehem, which later become the psychiatric hospital, Bedlam.
- Moving into Victorian Britain and the Industrial Revolution, the site become home to Broad Street Station from 1865 until it was closed and demolished in 1986.
- Following the demolition of the station, the Broadgate campus was formed as part of a new development looking to provide office space.
- Fast forward to the present day, and the new Broadgate campus is aiming to become a 7-day destination, not just for office space, but for retail and entertainment.
The Circular Economy means making sure that when materials are at the end of their life, we re-use or recycle them, instead of throwing them away. So how have we done that at 1 Broadgate? Have a listen to the following audio files to follow the journey of our 1 Broadgate materials from being removed from site, through to reuse –
To learn more about our Circular Economy strategy at 1 Broadgate, you can watch the following video.
What is the Circular Economy
Lowering the Fulcrum - Engineering Excellence
The Fulcrum is one of the most recognised sculptures in the city, sitting outside Liverpool Street Station. It’s a 55ft high sculpture, designed by Richard Serra, consisting of five huge sheets of Corten steel leaning against each other without any other structural connection. Part of the design brief for 100 Liverpool Street was to provide a level connection within the mall through to the future 1 Broadgate project which involved lowering the mall by 1.5 metres and, in conjunction with the artist, the decision was taken to lower the Fulcrum to sit on a new lowered base.
After discussion with the artist and the City of London Planning Committee it was decided to lower the Fulcrum insitu to preserve the integrity of the sculpture. This not only presented an engineering challenge but also a significant logistical challenge as it was in the centre of the main pedestrian exits to the station that couldn’t be closed.
The engineering solution involved installing new piled foundations under the Fulcrum to support a new lowered structural steel support frame. Using large, inverted jacks, to temporarily support the fulcrum and its base slab, the artwork was first lifted clear of the existing supports and then incrementally lowered onto its new base. This carefully monitored process took place over a period of two days and, to ensure the artwork remained upright during the lowering process, ballast was installed around the base of the fulcrum to lower its centre of gravity. Working with these logistical and technical constraints again highlights the engineering excellence that is embedded across our people and projects.
You can watch the lowering of the fulcrum in the video below.
If you want to know a little bit more about the engineering behind this and the works at 100 Liverpool Street, you can also watch the other video below from B1M.
1 Broadgate - Lowering the Fulcrum
Building a slipform core
Slipform is a construction method for reinforced concrete walls, generally lift and stair core walls, and is often economical for buildings more than ten storeys in height.
Slipform involves the formwork for the walls being raised in a continuous process as the wall concrete is poured. As the slip form rig is raised, it is supported by already cast concrete walls below. This animation shows how the slipform will be constructed.
Find out a little bit more about our slipform at 1 Broadgate:
The rig took 5 weeks to build
The finished structure will be 76m tall
From basement to floor 3, the floors vary in height
From floor 3, the height of the floors are 3.9m
There are 45 operatives working on the rig at one time
All work is continuous working – if we wanted to, we could pour the slipform in one go, working 24 hours a day!
Concrete must be placed within 2-3 hours as it cannot be used after this time
How many m3 of concrete do you think makes up the slipform at 1 Broadgate? Have a guess, and the closest answer will be in with a chance of winning £50 of Amazon vouchers! Email your guesses to email@example.com by April 15th.