Project Overview

Academy Geomatics was tasked with designing a monitoring scheme for a tunnel in the UK to ensure its stability during nearby construction works. Activities such as excavation, pile driving, and dewatering can change the stress state of the subsoil, increasing the risk of tunnel deformation.

To manage these risks and meet regulatory requirements, precise movement monitoring was essential. Academy Geomatics selected the proven method of tunnel convergence monitoring using an automated total station, providing real-time x, y, z displacement data of optical targets.

The Challenge

Installing automated total stations inside tunnels is not straightforward. Tunnel operators must guarantee clearance for vehicles, making them hesitant to place bulky equipment inside. Additionally, total stations require regular maintenance, meaning manual site visits that are both costly and cumbersome. That’s why other solutions for tunnel monitoring, such as tilt meters and laser scanning are becoming more popular.

Our Solution

Together with Academy Geomatics, we explored how TotaLite could perform under the harsh conditions of a tunnel environment.

• A TotaLite A1.0 sensor was installed next to the existing total station so both could observe the same optical targets.

• The system monitored three tunnel sections, each with five prisms, to reconstruct the tunnel shape.

• TotaLite requires a minimum spacing between targets of 2 degrees to avoid target overlap. Which means it can capture 3 sections without overlap and for any additional section another sensor is needed.
  
  

This pilot focused not only on accuracy, but also on robustness and the reduction of maintenance requirements.

The Results

The installation had to be done during a short tunnel shutdown together with other maintenance. However, due to straightforward setup and small device the installation went smoothly and within schedule.

Installation had to take place during a short planned tunnel closure, in parallel with other maintenance activities. Thanks to its compact design and straightforward setup, TotaLite was installed smoothly and on schedule.

Over three months of continuous data collection—with no site access required—TotaLite demonstrated:

• >95% uptime

• Accuracy within 2 mm, closely matching total station measurements

Based on this successful pilot, feedback was incorporated into the development of the next-generation TotaLite A2.0, offering improved accuracy, robustness in harsh tunnel conditions, and more plug-and-play data transmission.