The Gotthard Base Tunnel: an innovative journey to a world record (copy 1)

At 57 km long, the Gotthard Base Tunnel is the world’s longest tunnel and a key component of the Gotthard AlpTransit project. Passing directly under the Gotthard Mountain, this substantial development will enable a fast and efficient link between Zurich and Milan. By providing unique solutions to the challenges generated by such an enormous undertaking, Holcim has enabled the successful implementation of the project and created considerable value for its client.




High speed rail link between Zurich and Milan

The purpose of the Gotthard AlpTransit publicly funded CHF 9.7 billion (estimated) project under the Alps is to connect Zurich to Milan via a high speed rail link, thereby reducing the current journey time between the two cities for both passengers and heavy goods from 3h40mins to just 2h40mins. This reduction is provided both by the more direct route and the limited gradient and wide radius curves which will allow trains to reach speeds of up to 250km per hour. By providing an efficient means of transportation through the Alps it is expected that this project will significantly reduce road traffic through the region. Stemming from an idea dating as far back as 1947, the Gotthard AlpTransit Project proposals were granted approval in Switzerland in 1992. The project is owned by AlpTransit Gotthard which is a 50/50 joint venture between the Swiss state and Swiss Federal Railways, who are responsible for the overall running of the project.

 


The world’s longest tunnel

The Gotthard Base Tunnel consists of two single track tubes stretching between the north portal in Erstfeld - through Amsteg, Sedrun and Fadio - and the south portal in Bodio, each 57 km long. This makes it the world’s longest tunnel to date. With a rock overburden of 2300 m, it is also the world’s deepest railway development. To ensure passenger safety a total of 176 cross passages are placed at intervals of 325 m to enable travelers to exit the tunnel in case of emergency. Taking into account all cross-passages, access tunnels, and shafts the total length of the tunnel system is almost 152 km. To complete the continuous flat route necessary, the Gotthard tunnel is complemented by a 15.7 km long tunnel under the Ceneri.

 

Holcim’s scope of work

For the Bodio and Faido sections of the tunnel Holcim provided an integrated ready-mix concrete (RMX) solution fully tailored to the project. Holcim has set up a unique plant specially designed by its engineering experts. Its rail logistics enables the transport of the cement to the project site in a sustainable way. Holcim designed the high-tech RMX and supplied the total volume of 1.3 million m3 for these two sections. 100% of the required aggregates for concrete come from the recycling of the excavated material.

A consortium in which Holcim is involved was awarded the material management work package for Bodio, Faido and Amsteg, which includes the processing of excavated material into aggregates for concrete and the reutilization of the rest for other purposes. Furthermore, Holcim is also responsible for providing the cement required for the Sedrun section.


Project history and status of work

Excavation of the Gotthard tunnel took place between 2000 and 2011, with the opening scheduled for December 2016. Work on the Ceneri tunnel followed suit in 2007 and project completion is expected in 2019. The breakthrough in the excavation of the Gotthard Base Tunnel occurred in October 2010 in the east tube 30km from the south portal and 27 km from the north portal. This breakthrough occurred with a deviation of only 8cm horizontally and 1cm vertically, indicating the accuracy with which the excavation was conducted.

80% of the drive in the main tubes was cut using tunnel boring machines, with the remaining 20% excavated using traditional drilling and blasting methods. Upon completion of the excavation process in 2011 a total of 28.2 million metric tons of rock had been removed and transported from the tunnel, 12 million tons of which originated from the Bodio and Faido tunnel sections. Rather than simply being discarded however, a significant portion of this excavated material was utilized in order to produce 100% of the 2 million tons of aggregates necessary for the ready-mix concrete (RMX).  Material unsuitable for use as aggregates was used to form new railroad embankments and in the rehabilitation of a former pit.

In 2010, installation of the railway infrastructure began in the west tube between Bodio and Faido. This included the electric power supply, telecommunications, catenary, safety systems, and the track itself. As of November 2011 a total of almost 152 km of access passages, shafts, and tunnel had been excavated and much of the inner tunnel lining had been installed. 

Installation progress Railway technology, State 1. March 2015

 


Why Holcim?

Holcim was chosen as a partner on this project by the consortium TAT, the contractor for the combined main work package in Bodio and Faido, not only because of its expertise in cement, concrete, and aggregates but also due to the superior logistical capabilities offered by its rail linked plants in Siggenthal, Untervaz and Eclépens. By delivering an integrated solution, meaning that Holcim provides a single interface for the supply of cement, RMX and material management, Holcim is able to offer increased reliability and security. Holcim’s reputation for excellence in service, logistics and materials coupled with its early involvement in the pre-qualification test secured its participation in the project as a partner the client could trust.

 

© AlpTransit Gotthard AG



Overcoming project challenges

RMX plants

The decision to give Holcim the contract paid off. The RMX plants in Faido and Bodio were installed and in operation by March and July 2002 respectively. In the initial contract, a further RMX plant built on location inside the tunnel at Faido was deemed necessary in order to prevent concrete from setting before it reached its destination. However, the construction of a plant underground in a very confined space is both costly and time-consuming. By increasing the RMX setting time from six hours to eleven, Holcim enabled the transportation of RMX 30 km into the tunnel by rail. This was twice the distance which had been previously foreseen and meant RMX from the Bodio plant could be utilized for Faido as well, thus rendering the building of a further RMX plant unnecessary. Through this value engineering Holcim generated significant savings for its customer.

Holcim’s fully backed-up RMX plant at Bodio is in operation 24 hours a day and has the capacity to produce 120 m3 of RMX per hour. Technical lab and quality control tests for the materials used are conducted by Holcim, as is the dispatching of the RMX by rail to the remixing cars. To safeguard process reliability in the RMX production, surveillance was implemented through the installation of 25 cameras. Efficiency in the dispatch of the RMX produced, meanwhile, was ensured through the automatic filling of the rail cars at Bodio using four mobile overhead cranes. Each plant’s ecological performance is enhanced through the implementation of water recycling and noise isolation.

 

 

High-tech RMX

Holcim worked closely with its partners to ensure the flexibility necessary on site to be able to anticipate and rapidly react to changing circumstances and geological conditions. The requirement that 100% of the aggregates used be from recycled excavated material, for example, posed difficulties due to differences in their relative moisture and quality. To control for this, microwave sensors were installed in the aggregate silos and additives which were specially adapted to the varying aggregate compositions were used. As the temperature of aggregates needs to be in the range of 20oC to 25oC a heating system was also developed.  

These measures should ensure that the materials used possess the high level of durability required to last for the expected 100 year life span of the project. Two types of cement have been used for the tunnel profiles at Bodio and Faido, with CEM II/A-D 52.5 R being used for the floor, inner shell of the profile, and shotcrete, and CEM II/A-L 42.5 R for the filling, bench, and shotcrete. For the tunnel liner and bed the concrete used has a resistance class of B30/25, B35/45, or B40/30 depending on the application. The concrete used for the shotcrete meanwhile has a resistance class of B35/25 or B40/30, again depending on the application.

 

Logistics

The 400,000 tons of cement required were delivered by rail in a process carefully managed by Holcim from its rail connected plant in Siggenthal to Bodio and then fed into silos.

Due to the RMX and excavated material having to travel up to 30 km through the tunnel by train within a constrained time period efficient solutions were necessary. Specially designed RMX rail cars were therefore developed with the help of Holcim for this purpose.

© AlpTransit Gotthard AG


Project benefits

The reduction in journey time between Zurich and Milan of one hour represents a significant time saving. It is expected that this in combination with additional ticket sales of CHF 78 million and the CHF 76 million in revenue resulting from goods transportation will generate an annual return of CHF 400 million a year. What is more, with the transferal of heavy goods and private transport from road to rail Switzerland is implementing one of Europe’s largest environmental protection projects. The conservation of the delicate alpine environment through reduced road traffic should reduce environmental costs by CHF 130 million annually. In the process of achieving this, a total of 2600 people have been involved in the project development and implementation, generating employment opportunities and contributing to the economic development of the area.

Holcim has also contributed to this project’s sustainability through its rail-based logistics program, which not only also reduces road traffic and the subsequent carbon emissions generated but also improves safety levels. The recycling of aggregates, meanwhile, limits the amount of primary aggregate resources utilized by the project and serves to further reduce the need for road-based transportation. Thanks to Holcim’s innovative solutions to this project’s significant challenges then, the ongoing development continues to progress at an efficient pace whilst also following the principles of sustainable construction.