Monitoring for tunnels

The complete solution for monitoring in a tunnel environment

Urban Monitoring Use Case

The constantly evolving developments in towns and cities can congest areas leaving no space for future development or for the existing infrastructure and utilities to function. The solution in many urban areas is subterranean expansion such as tunnelling projects, creating space above and moving infrastructure below. However, these spaces are often hazardous environments, failure to monitor any affected areas or assets would endanger construction workers and any effected assets within the zone of influence of the tunnel.

Deformation monitoring provides real-time information about ground movements and tunnel distortions (e.g. displacement, ovalisation, convergence), allowing rapid and critical decisions to ensure the highest safety and effective risk management.

Total monitoring is the combination of data from geodetic monitoring sensors (total stations, GNSS, levelling or InSAR) with geotechnical and environmental sensors (tilt sensors, strain gauges, weather stations, etc.) and interferometric radar. It provides the complete picture about events occurring helping a greater understanding of the influence from construction or related activities. This is particularly critical when the tunnel excavation intersects with another tunnel structure, railway line, pipeline or passes beneath a heritage structure.

Why monitoring is beneficial in tunnels:

To record ground deformation before, during and after tunnel construction: excavation of the ground for a tunnel creates a low-pressure area which the surrounding material will attempt to move into to equalise. Therefore, a tunnel needs to support this to maintain its void.
Engineers can be informed about the normal movements of the ground, deformation during construction and longer term once the structure is completed. This allows engineers to balance changes in pressure, which may put a critical amount of strain and tension on the tunnel structure, preventing distortions or even collapse.
To protect adjacent assets: any excavation or construction that takes place near existing assets may cause movements that damage them, being aware of the first signs of movement via monitoring data allow for preventative/corrective actions. This is particularly critical when the tunnel excavation intersects with another tunnel structure, railway line, pipeline or passes beneath a heritage structure.
To detect changes in shape and structure during tunnel renovation: modernisation processes within the tunnel such as replacement or re-lining may introduce increased stress on the tunnel structure, causing movements or distortions. At this time it is critical to understand the effects of the works on the tunnel shape and structure.
To provide structural health monitoring: during the lifecycle of the structure from construction, assessing its performance and degradation over time, potentially extending the lifespan of structures or providing information for change in future designs.
To document historical change: Structural records associated with the deformation caused by tunnel construction or modification in case a disaster occurs.
To assess the impact of environmental change: upon the construction site and the inverse influence of the construction on the local environment.

This video presents typical generic examples of monitoring installations in a tunnel, yet every monitoring project requires its own specifically assessed and designed monitoring system thus specialists should be consulted before any installation.

Casestudies

Underneath King’s Cross redevelopment

Ensuring safety in London’s underground with a tailored monitoring solution

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View of Train at Sydney's Central Station being monitored by a Leica TM50 Total Station

Monitoring Australia's Biggest Transport Project

As excavation and construction barrel ahead on the Sydney Metro, a small and vital team of engineers have been quietly navigating the crowds and rumbling trains that define Sydney’s Central Station.

As excavation and construction barrel ahead on the Sydney Metro, a small and vital team of engineers have been quietly navigating the crowds and rumbling trains that define...

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