Tunnels
Excavation Begins on French End of 35-Mile Lyons-Turin Rail Tunnel
The Cenis base tunnel will account for most of the cross-border section of a rail line being built between Lyons, France and Turin, Italy.
Map courtesy of Tunnel Euralpin Lyon Turin
Work on the French portal of the 35-mile twin rail tunnels under the Cenis Mountain has just begun as part of the planned 170-mile Lyons-Turin railroad. Nearly a fifth of the 100 miles of access and running tunnels have been completed through the Alps on a construction program scheduled for completion in 2032.
From a cut-and-cover approach at Villard-Clément on the French side, a joint venture led by Swiss-based Implenia A.G. has just started forming 1.7 miles of twin tunnels with excavators and drill-and-blast. Excavations will reach a 6.5-mile section of the south running tunnel previously completed for tunnel boring machine (TBM) trials between Saint-Martin-la-Porte and La Praz.
Opening the first portal "is a further step forward after the signing [in 2021] of the tenders for the construction of the base tunnel on the French side worth $3 billion," says Emmanuel Humbert, deputy director for construction at the project owner Tunnel Euralpin Lyon Turin.
"With the next award of the contracts for the Italian side ... in 2023, the construction phase will enter a new stage, with the aim of having the line operational in 2032," Humbert adds.
The Cenis base tunnel will have two bores with 27.5-ft-internal diameter and up to 6,560-ft of overburden. The bores will be set between 100 ft and 260 ft apart and be linked with cross passages at 1,100-ft intervals. Nearly 80% of the base tunnel will cross French territory.
Estimated to cost $9.1 billion, the cross-border portion is 40% financed by the European Union, 35% by Italy and 25% by France. TELT is equally owned by French and Italian state entities.
With extensive access and investigation excavations completed at sites along the route over the last two decades, TELT signed three contracts for the main tunneling in France in July 2021.
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The 72-month contract covering the French portal, valued at $244 million, includes the short Saint-Julien-Montdenis to Saint-Martin-la-Porte section. It runs into another contract, by a team led by VINCI Construction Grands Projets. Valued at $1.5 billion, this 65-month contract, covering 14 miles of tunnel between Saint-Martin-la-Porte/La Praz and Modan, will deploy three TBMs.
The most easterly contract will complete the final 14 miles to the Italian border, using two TBMs. A joint venture led by EIFFAGE Génie Civil secured the contract with a value of $1.6 billion.
With nearly a fifth off all the tunneling completed and work on the main drives building up, a team led by VINCI this October began the first pilot holes for raise boring four 1,640-ft-deep ventilation shafts at Avrieux. Under a $235-million, 36-month contract, the team will bore four 17-ft-diameter shafts roughly half way along the route.
Meanwhile, as teams in Italy prepare to sign a $1 billion of tunneling work, a battery-powered robot has completed a survey of potentially dangerous gases in the final 1.9 miles of the existing 4.7-mile Maddalena pilot tunnel at Chiomonte, west of Turin. The Webuild Group used the machine to assess the tunnel’s condition after it lay idle for five years.
