Mixshield: Maximum safety
in mixed ground.
Fluid-supported Mixshields are specialists for multi-layered, complex geologies, particularly those with a high water content. In heterogeneous geology, the machine can be operated as required in the slurry or Mixshield modes, thanks to its modular assembly design. In addition, it is technically possible to operate with a combination of Mixshields and other shields. All combinations of slurry, earth pressure balance, compressed air or open shield methods are generally possible with convertible Mixshields.
Shanghai, China
A reference project with worldwide significance. Since September / December 2006, our largest 15.43 meter diameter tunnel boring machines are at work underground in Shanghai. The S-317 and S-318 Mixshields are tunnelling two three-lane motorway tubes, each 7.47km long, under the booming metropolis. Their task is to link the district of Pudong with Chongming which is to be a large "green" island in the Yangtze delta. In April 2010, this major tunnel will open to traffic.
Download the project folder S-317/318.
Hallandsås, Sweden
The route through the Hallandsås mountain ridge in Southern Sweden is regarded as one of the most difficult tunnelling projects in the world. A consortium composed of the Skanska and Vinci companies set to work in March 2004 to find a new way of cracking this particularly hard nut. Two tubes, each 5.6km in length, are needed and for this, Herrenknecht engineers have developed and built a convertible Mixshield with a diameter of 10,530 millimeters. Depending on the conditions in the Hallandsås Mountains, it can be operated in safety as an open hard rock machine or in closed mode - with slurry support - if groundwater pressure is high.
4th tube for the Elbe Tunnel, Hamburg, Germany
For German shipping, Hamburg is the gateway to the world and the Elbe is the access route to the North Sea and the Channel. The Elbe tunnel passes under the river and to maintain its role as a vital traffic artery, it needs a fourth tube. Trenchless tunnelling is the only option if shipping is to pass unhindered. Enter "Trude", an acronym for the German phrase meaning "deep down under the Elbe" which, with a diameter of 14.2m, is one of the largest Mixshields in the world. The challenges to be overcome by "Trude" are unprecedented since overburdens are sometimes only seven meters, pressures are of up to 5.5 bar.
The monster comes packed with numerous innovations. To enable rapid and safe tool changes in underground atmospheric conditions, the cutting wheel was fitted with accessible spokes. Also, the active center cutter can be operated independently of the cutting wheel, which prevents clogging in the center of the cutting wheel. "Trude" is the first to benefit from the SSP system (sonic probing) which enables it to "foresee" the complex soil conditions up to 40m in front of the cutting wheel. This will enable "Trude" to emerge at the end as planned after 2,561m - yet another vital milestone in Herrenknecht's tunnelling and Mixshield technology journey.
