ECTC: A Complex & Creative Project

Morrisroe’s work on the Elephant and Castle Town Centre (ECTC) development forms part of a wider transformation of the area and involves complex works requiring a healthy dose of creativity.

The development is being delivered in three phases. The current one includes the iconic Shopping Centre which was the first ever covered shopping area in Europe. It will be home to the London College of Communication (part of the University of the Arts), several new retail, office and residential units, a cinema, and a new expanded underground station.   

Our extensive package of works, which began on site in January 2022, includes the construction of a highly complex two-storey main basement and five-storey London Underground (LUL) basement box / integrated ticket hall. This will involve extensive piling, the construction of piled capped raft slabs and hybrid top-down construction methodology over the LUL ticket hall. The four towers will see the construction of jumpformed cores and PT slabs above podium level.  

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Ground Engineering

Ground engineering works (along with our 4D model) have revealed the complexity of the project. This is mainly due to the links with LUL, the five-storey deep basement box for the integrated ticket hall – which is effectively split into two halves to allow for trains to enter and will be excavated down to an impressive 28 m below street level – and space to allow for the future extension of the Bakerloo line.

Buildability and specific construction methods were decided after an extensive design review focused on London Underground exclusion zones that sit within the site's footprint. As a result, more than 400 secant and contiguous piles were used to support and safeguard LUL tunnels. We have piled over Bakerloo line tunnels, going within 1.5 m of the crown of the tunnels. The project’s construction specialist Multiplex subsequently piled along the flanks, going approximately a couple of metres below the tunnels.  

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The ground conditions added further challenges, particularly the Harwich Formation layer and its significant hydrostatic pressure. “In the Harwich layer, most of the piles are temporary segmental cased, other than the bearing piles. For the secant wall, we’re driving segmented casing down to seal off this Harwich layer,” Morrisroe Operations Director Mark Wadsworth recently told Ground Engineering.

“And that’s where the casing should cut in advance of the auger, but this Harwich layer was so thick at times that the auger is needed to almost try and break it. But the idea is that we case down, and at that point we’re below the entire asset. So, in terms of any support fluid loss or water ingress to the tunnels or the stations, that negates them.”

Directly employing a competent workforce familiar with these kinds of ground conditions has been of great benefit during such a challenging process.

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A Bespoke Process

Classic “blue sky” construction is being used for most of the site. But one residential tower building also uses a “top down” sequence. “It is like a box in two halves, so one half is across the tunnels and the other half is top down from B2. So, we’ve got the traditional basement down at B2 almost across the entire site, then the other half going down another three levels,” Wadsworth added to Ground Engineering.

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The atrium of the UAL building provides further complexity due to the bespoke loading requirements of each floor. The geometry of the atrium will also change at each level, requiring a distinctive temporary works and propping solution in line with our previous work on the Library of Birmingham.

Our work on the development is scheduled to complete in the summer of 2024.  

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