A wide-ranging Instrumentation and Monitoring scheme for an new office development combining manual surveying, automated 3D surveying, geotechnical, and environmental monitoring.
The project
The Dovetail Building will be a 23‑storey office development near to the City and Spitalfields. Designed as a flexible and sustainable workplace including amenities, retail, and public realm spaces.
Early stages of the project require significant demolition and excavation works
The challenge
The location of the project is already heavily developed and the site is surrounded by existing buildings and infrastructure. The monitoring scheme must adequately measure the impact of construction works on the surrounding buildings, nearby streets and TFL Underground tunnels.
The solution
At street level, survey teams are carrying out manual 3D monitoring of structures and assets surrounding the site as well as precise levelling across adjacent roads and pavements to small movements that could indicate settlement, deflection or other structural changes during the works.
Around the perimeter of the development, 24 hour monitoring of noise, dust and vibration is achieved with automated environmental sensors.
The system includes sensors recording dust (PM10) concentrations, alongside vibration sensors and noise monitors.
These instruments provide continuous data, helping the project team understand construction impacts in real time and ensure activities remain within required limits.
Additionally, twelve 25-metre manual inclinometers will be installed in the wall around the excavation to further supplement the monitoring scheme. These inclinometers will be read manually throughout key construction phases.
Below the surface, alongside the site, additional monitoring is taking place within a London Underground tunnel and along the operational railway tracks. Two automated total stations have been installed in the tunnel, taking regular readings from more than 100 geodetic prisms fixed to the tunnel lining.
In order to achieve line of sight to all the necessary monitoring locations while adhering to strict limitations on clearance inside the tunnel, bespoke brackets were designed and fabricated to mount the total stations above the tracks on the crown of the tunnel.
Readings from both total stations are processed as a common prism network via QuickAdjust, a module of GEO-Instruments' QuickView software platform. This module automates the StarNet least-squares adjustment and feeds calculated values directly into QuickView for visualisation alongside the project’s other monitoring data.
Track trolley surveys are also carried out by surveyors at key phases of construction. These track geometry surveys capture changes in the shape and alignment of the rails and measurements are processed to calculate parameters such as gauge, cant and twist.
These manual track surveys, that can only be carried out at night during TfL engineering hours, are vital for detecting developing movement in the tracks before issues arise.
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