A wide-ranging Instrumentation and Monitoring (I&M) programme is underway at the Dovetail Building, an impressive new office development in central London.
The scheme combines manual surveying, automated 3D surveying, geotechnical, and environmental monitoring to measure the impact of construction works on the surrounding buildings, nearby streets and TFL Underground tunnels.
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.
The project involves significant demolition and excavation works that require a thorough and detailed monitoring scheme.
Street-Level Monitoring
At street level, survey teams are carrying out twice weekly manual 3D monitoring of structures and assets surrounding the site. This includes observations of prisms and retro targets installed on neighbouring buildings, as well as precise levelling across adjacent roads and pavements.
The survey scheme is designed to detect 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 multiple HIVE-AQ Dustroid sensors recording dust (PM10) concentrations, alongside HIVE-VIBE Swarm vibration sensors and SV 307A noise monitors.
These instruments provide continuous data, helping the project team understand construction impacts in real time and ensure activities remain within required limits.
As the works progress, the scope of the manual surveying is expanding to include monitoring of the capping beam.
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 at least twice a week throughout key construction phases.
Tunnel Monitoring
Below the surface, alongside the site, additional monitoring is taking place within a London Underground tunnel and along the operational railway tracks.
Two Leica Geosystems TM60 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 had to be 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.
In addition to automated 3D prism monitoring, track trolley surveys are 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.
The tunnel monitoring programme is supported by condition surveys of the tunnel interiors and tracks carried out before site works began. These inspections help establish baseline conditions and provide a reliable record for comparison as the project progresses. Follow-up surveys will be undertaken at later stages of construction.
Together, the combination of automated instrumentation, manual surveying and environmental sensors provides a detailed picture of the project’s effect on nearby buildings and the transport network.
Find out more about our construction monitoring projects.