MC Know-how for Stuttgart 21 - the Albvorland Tunnel

For the Stuttgart 21 megaproject, MC was able to contribute both its expertise and its bespoke product systems for tunnel construction from its Tunnelling Field of Expertise, all very much to the satisfaction of its clients. In cooperation with planning engineers and construction companies, the tunnel experts at MC also developed innovative solutions optimally adapted to the various requirement profiles and challenges encountered on site, thus further facilitating the smooth progress of the tunnel projects.

A German megaproject

With a spend of around 8 billion euros, the transformational Stuttgart 21 transport and urban development project will greatly benefit the local region through the creation in the near future of a major hub in the national – and international – railway network. More than 100 km of new, fast railway track, three new stations and an intelligent traffic management concept will set new standards in domestic German and European rail transport going forward. And there will also be major benefits on the urban planning side: About one square kilometre of current or former track sections on the edge of Stuttgart's city centre are to be put to good use in the project, extending the downtown area by around 40 percent. 

 

MC’s expertise in mechanical tunnel excavation in high demand

The heading operation with lining segment installation was conducted using a full-thickness-cutting shield TBM featuring multi-mode earth pressure balance (EPB) for face support. The Albvorland Tunnel was only one of several major tunnel projects involving MC that were mechanically excavated. Various MC technologies and product systems were used in all the tunnel construction projects, including special products for soil conditioning, superplasticisers for lining segment production, injection systems for waterproofing the tunnels and, last but not least, a completely new, cement-free annular gap backfill grout – an innovation successfully developed in harness with the special-purpose consortium ARGE ATCOST 21.

 

A similar tunnel construction approach was also adopted in the case of the Albvorland Tunnel. Here again, two tunnel tubes with a diameter of 10.87 m and an overburden of between 8 and 63 m were excavated over a length of around 8,000 m.

 

Optimised bedding properties

The experience gained from the development of the modified 2C annular gap grout was also used to adapt a classic 1C annular gap mortar at the Albvorland Tunnel between Wendlingen and Kirchheim unter Teck. Because the rate of TBM advance had increased there, a faster means of grouting of the tunnel tube had become necessary, something that was beyond the conventional 1C mortar being used. For this purpose, MC-Bauchemie developed the consistency modifier MC-Montan Grout 05. As an additional component, it is added to the mortar via a mixing section during the injection phase, but prior to pilaster strip entry, ensur-

ing optimum bedding properties. As with S21, it also eliminates the risk of subsidence where heading performance is accelerated. The modified grout was applied continuously in parallel to the soil conditioning work over a length of 8 km at the Albvorland Tunnel.

Ideal lubrication

The most widely used soil conditioning agent was MC-Montan Drive FL 04 (Foam Liquid), an environmentally compatible and readily biodegradable foam concentrate with a defined proportion of clay additive. The product is ideally suited for soil conditioning in EPB tunnelling as well as in rock formations with a high clay content and a high likelihood of clogging. Economical in use, MC-Montan Drive FL 04 prevents deposition and agglomeration and increases the lubrication effect by dispersing the clay minerals. By repelling spoil and preventing accumulation at the cutter head, the agent also reduces TBM power consumption and cutting tool wear.  Thus the soil conditioning solutions from MC were able to increase heading efficiency as well as satisfy strict cost-efficiency requirements.