Delivering instrumentation and monitoring for Bertha Park Link A9/A85 Perth Junction

Balfour Beatty is delivering the first phase of Perth’s major new transport infrastructure improvements. ITM Monitoring, now SOCOTEC Monitoring UK Ltd, was selected to deliver the instrumentation and monitoring for the construction phase of the project.

With many layers of subcontractors, teamwork and frequent communications were as critical in ensuring the project ran smoothly as the design and installation of the monitoring system.

Project Overview

Phase 1 of the Perth Transport Futures Project is to provide a new link road from the A85 Crieff Road across the A9 dual carriageway and River Almond into Bertha Park.  This link road will provide access to the proposed secondary school at Bertha Park.  It also will provide some immediate benefits to and from the Industrial Estate and at Inveralmond Roundabout.
The scheme will also deliver improvements for pedestrians and cyclists, including a shared-use cycle/footway for the whole length of the new link road, a new footbridge over the A9 north of the new grade separated junction, a new path along the diverted Lade stream and Toucan crossings at all new traffic signal junctions.  Additionally, an overflow car park will be created at the local crematorium.

The Approach

Since October 2016, when the project commenced, ITM has provided comprehensive ground investigation works and has been monitoring the new road embankments through the installation of geotechnical and structural instrumentation measuring the water pressure, settlement and strata behaviour.

To enable the client to obtain knowledge of the impact on local assets, inclinometers were installed along the A9 to monitor the effect of the new build on the existing road.  Due to the proximity to the River Almond, ITM installed piezometers for measuring the pore water pressure and in addition, hydrostatic profile gauges and rod and plate gauges were used to record settlement.
Balfour Beatty site staff received training from ITM on how to manually read the piezometers and loggers which were installed at the greenfield site.

The seasonal weather posed challenges due to the cold and reduced available daylight. However, ITM actually found that the frozen ground made access to the site easier considering the high volume of mobile plant on site and it focused the team’s efforts to make the most of the short daylight hours.

As is often the way when there are multiple layers of subcontractors involved in completing the job, ensuring a joined-up approach is essential. Open lines of communications and some education around the purpose and function of the monitoring system all helped to build rapport and understanding between client, subcontractors and ITM, reducing the likelihood of accidental damage to equipment and resultant project delays, which contributed to a constructive working atmosphere.

Instrumentation Used:
Vibrating Wire Piezometers
Vibrating Wire Data loggers
Hydrostatic Profile Gauges (29-83m)
Rod and Plate Settlement Gauges
Vertical Inclinometers