Ceneri Base Tunnel: a journey under the Alps

Author: Grace Goss-Durant

The Ceneri Base Tunnel builds on ideas dating as far back as 1947, when the concept of constructing a tunnel to enable easy and efficient transport through this area of the Alps was first introduced. Through its tailored, integrated logistics and materials solution, Holcim is helping to make this vision a reality.

A key development in the European High Speed Network, the central aspect of the Gotthard AlpTransit Project consists of two separate rail tunnels passing under the Gotthard and Ceneri mountains to connect Zurich and Milan. With minimal gradients and wide-radius curves, this high speed rail link will reach up to 250 km per hour and reduce the current journey time between the two cities by approximately 60 minutes. Excavation of the Gotthard Base Tunnel began in 2000 and work on the Ceneri Base Tunnel followed suit in 2007. Project completion is expected in 2019 at an estimated total cost of CHF 2.4 billion.



RMX inside the mountain

At 57 km, the Gotthard Base Tunnel is the world’s longest tunnel. Without the completion of its 15.4 km counterpart under the Ceneri, however, a continuous flat route through the Alps would not be possible. Stretching between Vigana and Vezia in the Swiss Canton of Ticino, the Ceneri flat rail route will carry both passengers and cargo and is intended to significantly reduce the amount of road traffic through the region as a result.

Almost 100 percent of the cement and most of the primary aggregates and concrete needed for the tunnel lining and bed are being supplied by Holcim, who provide logistical as well as materials solutions to the challenges of the development. 

Upon project completion, a total of 7.9 million tonnes of material will have been excavated, transported via conveyor belt from the tunnel at Sigrino, and separated into landfill material or recycled as aggregates for concrete. Around 0.4 million tonnes of aggregates for this project will be produced in this way, with another 1.6 million tonnes of primary aggregates delivered via train by Holcim from its Hüntwangen quarry. The cement itself, circa 390,000 tonnes, is supplied from Holcim’s plants at Siggenthal and Eclépens.

Each day, 800 m3 of ready-mix concrete (RMX) is required onsite. In order to provide this, a specially designed RMX plant was installed by Holcim 2.3 km into the mountain at Sigirino. The production of concrete began in 2010, and as of March 2015 almost 90 percent of the tunnel had been excavated by conventional drilling and blasting methods. Progress has not been without difficulties however, with excavations being delayed in 2011 due to challenges presented by the geological make-up of the southern area of the tunnel.

© AlpTransit Gotthard Ltd
© AlpTransit Gotthard Ltd


"Outstanding know-how"

Holcim was chosen as a partner on this project due to its expertise in logistics, engineering, and materials and its capacity to deliver an integrated solution tailored to customer needs. Its previous successful involvement in the construction of the Gotthard Base Tunnel also played an important role. According to Federico Cognigni, Head of Concrete and Raw Materials at the project’s main contractor, Condotte Cossi, “the Ceneri Base Tunnel is a very large project over a long time period, and it is therefore very important for us to have a partner who not only delivers the raw materials, but also supports us in resolving problems.”

Through its rail-linked plants, Holcim is able to offer reliable high-performance logistical solutions. Furthermore, the fact that Holcim offers all solutions in-house means that a higher level of security and reliability can be reached. As a company well-represented throughout Switzerland and the wider world, Holcim is a trusted business partner. Holcim has outstanding know-how in engineering," says Cognigni. "To date Holcim has built, supervised, and managed more than 40 RMX plants in Switzerland. The company also has extensive international contacts, with plants throughout the world.”

 

Tunneling through challenges

In order to meet the significant challenges such an enormous undertaking in difficult geological conditions involves, specially adapted concrete mixes had to be developed. All the recipes had to be resistant to alkali aggregate reaction (ARR) and have the ability to function without difficulty at high ambient temperatures. Holcim therefore developed a cement type tailored to offer early strength, high impermeability, and chemical, fire, and shrinkage resistance.

The tunnel itself is expected to have a lifecycle of a hundred years, and this also had to be considered when choosing materials. Perhaps most challenging however was the designing, building, and commissioning of an RMX plant 2.3 km into the mountain in an extremely confined space and within a ten month deadline. The construction of this plant, equipped with heating and moisture sensors for aggregates, self-cleaning cement silo, scale, and mixer filters, a collection pan for contaminated water, water recycling system, and an electrically operated compressor for the loading of silos, was achieved through the mobilization of Holcim’s advanced engineering capabilities and expertise.

In order to guarantee continued supply, the plant has two independent mixers operated from separate control units. The RMX plant is in constant operation, and the Holcim crew works in teams of two for three shifts lasting eight hours each. Safety is a top priority, with the special conditions present in working underground demanding careful planning in terms of equipment and logistics. The effective communication and coordination of staff is essential to ensure both security and efficient service. Moreover, Holcim’s close working relationship with project partners and the flexibility provided onsite means that it is possible to react rapidly to changing circumstances.


An alpine advantage

It is estimated that through additional ticket sales amounting to CHF 78 million per year and the significant time saving offered by this high speed link, this project will generate an annual return of CHF 400 million. Goods transportation will contribute another CHF 76 million in extra revenue. Furthermore, in constructing the Gotthard AlpTransit Project Switzerland is implementing one of Europe’s largest environmental protection projects. By diverting heavy goods transport away from the roads, damage to the delicate alpine environment will be substantially reduced. This in turn should decrease estimated environmental costs by CHF 130 million per year. Moreover, the onsite recycling of excavated material for use as aggregates significantly reduces resource use and the need for transportation. By diverting transport from road to rail, Holcim’s implementation of its logistics program further adds to the project’s sustainable development credentials - and also increases safety levels.

During the entire construction process, Holcim has been able to provide continuous supply, adapt to the needs of the project, and meet vital deadlines. As Cognigni points out, “it is very important to have partners with outstanding continuity and performance over the long term.” Through its expertise and experience, Holcim continues to deliver on this.