This new, mixed-us development on the site of the former New Scotland Yard building in Westminster, comprises of two podium structures between ground and fourth floor, with each supporting three towers that range in height from 14 to 20 storeys. A new three storey deep basement over the full site area, will extend beyond the depth of the existing single storey basement, and provide plant areas, cycle storage and car parking spaced, and at lower ground floor will incorporate spa and swimming pool facilities.
The site contained over 300 existing piles, including underreamed piles, from the previous development, many in locations which could not be defined during the design stage. This provided a challenge for the location of new piles and would typically necessitate the extraction of existing piles to give a buildable scheme. The approach of the RBG’s geotechnical team was to develop a pile-assisted raft solution that was delivered by undertaking 3D finite element modelling. This significantly reduced the number of piles required compared to a fully piled scheme and was key to the viability of the project programme, since it eliminated the requirement to remove the existing piles. This proposal also de-risked the project by allowing flexibility in the location of new piles when clashes occurred due to existing piles being out of position when compared to the record drawings.
With a perimeter of over 350m, the new basement is extensive, and as such, its excavation was a significant item on the construction programme. The site boundary is surrounded by a multitude of sensitive buried utilities, live carriageways and nearby buildings for which ground movement was a key consideration. To accelerate construction while controlling ground movement, RBG developed a detailed construction sequence using partial top-down construction that minimised temporary propping and provided a ground floor slab early in the programme to be used for logistical access and lay-down of materials. This included full geotechnical design of the perimeter retaining system and all associated temporary works.
RBG Geotechnical Services
- Ground investigation works,
- Retaining walls and temporary ground stability,
- Temporary works,
- Design of piled raft,
- Soil-structure interaction modelling,
- Excavation sequencing,
- Monitoring of retaining walls and existing buildings.
GBP £400 million
Retail: 4,039m2 GEA
Office: 14,826m2 GEA
Residential: 49,638m2 GEA
Squire & Partners
Robert Bird Group Services:
Construction Engineering (seperate contracts for Main Contractor and Enabling Works Contractor)