GEO-Instruments worked alongside colleagues from Keller on the £90m redevelopment of the iconic Westbury Mayfair Hotel in London.
The project
The redevelopment will provide 196 rooms and suites through the addition of an eighth floor, an extension to the rear of the hotel and enhancement of the façade and public areas of the building
Keller’s foundations division is working with main contractor Sir Robert McAlpine on a number of construction elements, which are being monitored for ground movement by engineers from GEO-Instruments.
The challenge
Keller's tasks include constructing a 32m long 600mm diameter secant piled wall to provide an extension to the rear of the existing hotel and, internally,104No 300mm restricted access bearing mini piles to new cores to support a variety of other pits and walls.
There are also 106No plunge circular hollow section mini piles to underpin 26 existing columns to create a new deeper double-storey basement beneath the existing structure.
These significant excavation works require comprehensive daily monitoring.
The solution
GEO-Instruments have installed a system of manually monitored inclinometers within the secant wall to a depth of 16m in order to monitor the deformation of the wall as excavation works progress. Settlement studs have also been installed to monitor the movement of the site’s extremities. Read manually using an ATS and mini prism, these points are compared to an array of reference points fixed to surrounding buildings.
Both systems are surveyed twice weekly and additional prisms will be installed along the top of the wall’s capping beam once complete, supplementing the existing surveys.
GEO-Instruments are also providing full reporting and visualisation of monitoring data via its QuickView software.
