That was the challenge behind the microtunnelling project which has just been completed on the banks of Lake Annecy.
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- A 328 metre long curved microtunnel, using an HK AVN1200
- Crossing beneath the river Thiou, the Jardins de l’Europe and the Canal de Vassé
- Tunnelling up to 13 m below ground level
- Mixed ground conditions with very soft clay on entry and over most of the drive, and gravels / cobbles near the exit
Faced with the complex ground conditions and significant environmental constraints, digging a trench was clearly not an option. The trenchless solution limited disruption and helped protect the site’s many protected trees.
OPTIMUM has been supporting the Grand Annecy authority since 2021, from the first feasibility and design of the microtunnel, through to on-site supervision. And when challenges arose during shaft construction, OPTIMUM specialists stepped in with targeted adaptations.
The result ?
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- The shafts were successfully completed, the microtunnelling works got underway, and the drive was finished in record time – 225mm / min average tunneling rate – thanks to great work from SADE.
The real value of technical expertise lies not only in designing the right solution, but in being there to keep the project moving when challenges arise.
