Abstract

Land Securities are nearing completion of redeveloping the site known as One New Change located on the south side of Cheapside in the City of London. The site is located approximately 60m to the east of St. Paul’s Cathedral. Arup has been closely involved with the project since 2004 acting as structural and geotechnical consultants for the development.

The new development involved initially demolishing an office block that occupied the site, then excavation of a new basement that extends to approximately 14m below ground level, while concurrently constructing the new superstructure. The construction of the new basement and structure above has caused unloading and subsequent reloading of the ground.

The presentation will initially provide a brief overview of the development and provide a summary of the findings from the desk study and site investigation carried out to establish the ground and groundwater conditions. The geotechnical design will then be discussed identifying issues relating to the design of the basement and piled foundations.

The remainder of the presentation will consider several planning constraints placed on the development that Arup played a key role in addressing. These include:

• Design and installation of the ground source heat system comprising open loop pump and recharge wells and closed loop piles. This addressed the renewable energy requirement placed on the development under the planning conditions

• Groundwater modelling carried out to address the requirements of the St Paul’s Depth Act

• Assessment of impacts on the nearby London Underground Central Line tunnels that run parallel to the northern boundary of the site.

For the latter two assessments, comparisons will be made between the modelling and monitoring results collected during the works. Conclusions will be drawn from these comparisons.

The presenter, Mike Devriendt is a geotechnical and tunnelling engineer who has worked for Arup since 1997. Mike is currently working on the Crossrail project in London.