Aldgate Union
When facing the second phase of large-diameter auger (LDA) piling at 1, Aldgate Union, leading geotechnical specialist Bachy Soletanche faced a unique question; How can a one hundred tonne piling rig be mobilised onto a site that has an underground shopping centre directly underneath? Without extra support, the ceiling of the disused Aldgate Union Shopping Centre risked collapse when the weighty Bachy Soletanche rig sat directly above, constructing LDA piles up to thirty-five metres deep.
Barry Osborn, Contract Manager at Bachy Soletanche explained how the problem was solved:
“The weight issues at Aldgate Union provided an obstacle that was completely unique to the site. A solution was developed that supported the ceiling of the underground shopping centre using a combination of mini-piling and props. The added support allowed us to mobilise the LDA rig onto the site above and complete the piling that was required to support the new building being constructed.”
The mini-piling helped to provide support for the floor of the underground shopping centre, which could then carry the weight held by a forest of props carefully positioned to support the ceiling of the complex. Once this support process had taken place, Bachy Soletanche was able to commence the LDA piling above.
In total, the £500,000 contract involved the construction of six 2.1m diameter piles with under-reams up to 5.5m in diameter, and three 2.4m diameter piles that required the rig to situated directly above the underground shopping centre due to their position. With up to 140m3 of concrete in each pile, the time taken to construct these large piles meant long hours for the Bachy Soletanche site team who worked late into the night on a number of occasions.
Bachy Soletanche completed the piling work for the new office-block development at 1, Aldgate Union on March 17th.