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A9 Dualling: Pipe Jacking in Preparation for Bridge Replacement

Iseki Unclemole Super TCS1200 TBM - A9 Dualling

The current work of Network Rail is, excavating through a railway embankment at Lynebeg in the Scottish Highlands, cause it is a part of advance works for Transport Scotland’s A9 Dualling Tomatin to Moy project.

Reconstruction of a rail bridge near Moy, is the next duty of the Network Rail engineers. Building a new underbridge for the railway and undertrack utility services includes these works.

In order to accommodate interim utility diversions during the demolition of the existing structure, and the installation of the new wider railway bridge, constructing an under track crossing was one of the main and initial tasks of the project. Longer-term it will also serve as an overflow outfall for an ecology pond being created adjacent to the track.

Network Rail’s solution for reducing the disruption for rail passengers, was purchasing an Iseki Unclemole Super TCS1200 tunnel boring machine (TBM), which was tunneled 33m beneath the railway to break through a mixture of sand, gravel, and rock over a period of four days.

A channel for eleven 1,200mm diameter, 2.5m long concrete pipes, that was placed and installed using a hydraulic jack, was run into the railway embankment by the hydraulic drilling machine. Eleven concrete pipe sections were installed under the railway in total.

Because of the required depth through the embankment, the usual method of deleting track sections and excavating would have caused major disruption on the railway line. According to Network Rail, while pipe sections installation was pursued, the TBM allowed the trains to continue to run. Embankment and track monitoring were carried out simultaneously.

Network Rail project manager on the Lynebeg bridge replacement project, Malcolm McGowan, said: “Finding ways to carry out work on the railway in a way that minimizes disruption to train services is a fundamental part of our planning process and shows how we are putting passengers first.”

He continued: “By bringing in the ‘mole’ tunnel boring machine to excavate the channel under the railway and the hydraulic jacking rig to position the pipes, we could get the job done efficiently while keeping the line open to traffic. We are at the early stages of the project but are looking forward to sharing more details about the work and engaging with the wider community as we move forward.”

“Undertaking these works in advance of the main construction contract to dual the A9 between Tomatin and Moy helps to provide more certainty to our contractors’ program for the main works contract,” added A9 Dualling Tomatin to Nick Conroy, Moy project manager.

The Scottish Government pays special attention to the process of replacement of the railway bridge at Lynebeg due to dual the A9 between Perth and Inverness.

Previous week Graeme Dey, the Scottish minister for transport, commenced the procurement process to choose the main contractor to construct the £115M section of the A9 Dualling program between Tomatin and Moy.

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