Gripper TBM: with heavy metal
through hard rock.
For use in solid rock, the principle of the gripper is both the most simple and most effective technique. The single gripper machine braces itself against the rock using two gripper plates. Then, hydraulic cylinders push the cutterhead into the tunnel face at high pressure, grinding it with cutter rings. Double gripper machines work according to the same principle, using four hydraulically operated gripper plates.
Gotthard Base Tunnel, Switzerland
With two 57km-long tunnels, the Gotthard Base Tunnels will be the world's longest railway tunnel. Four Herrenknecht Gripper machines are excavating a total of 75km through the Alps. The identical S-210 and S-211 (diameter of 8.830m each) have been cutting their way through the rock from the south since November 2002 and February 2003 respectively. After almost 4 years, on 6th September 2006, the S-210 broke through to "Faido" multifunctional station in the eastern tunnel. On 26th October, the S-211 caught up and reached the milestone with utmost precision after drilling through almost 15km and extremely difficult geological conditions. Since the two Herrenknecht Gripper machines S-229 and S-230 (diameter 9.580 each) coming from the North reached their job lot in the Amsteg section in June and October 2006 respectively, TBM excavation has been paused. It is scheduled to resume in mid 2007.
The S-210 and S-211 machines are being overhauled in the tunnel. This includes complete dismantling all relevant components and enlarging them by 60cm. Afterwards, the two TBMs will be excavating the last long section between Faido and Sedrun with a boring diameter of 9.43m and another 12km through the mountain.
Tunnel Maurice Lemaire, France
The longest road tunnel exclusively running on French territory links the villages of Saint-Marie-aux-Mines and Lusse in the Vosges mountains. An emergency tunnel of approx. 6.2km running parallel to the main tunnel was excavated using a Herrenknecht Gripper TBM with open hard rock shield. This is the first time that this type of TBM has been used in France. The TBM, which had been commissioned by JV Bouygues Eiffage TP started excavation on the Alsatian side in February 2005. The tunnel ran through gneis and granite at a distance of around 16m from the main tunnel. With a maximum weekly advance of nearly 234m and a daily record of more than 55m, the machine reached the target near Lusse on 2nd June 2006. The "Maurice Lemaire" road tunnel has been modernized and is scheduled for reopening before the winter 2007/2008.
West Area CSO Tunnel, Atlanta, USA
Since 2005, two Herrenknecht Gripper TBMs with a diameter of 8.23m each have been excavating gneis. The two storage tunnels (CSO, Combined Sewer Overflows) are going to be a total length of 13.4km and will have a capacity of almost 700 million liters of mixed water once they have been completed at the end of 2007. The water which collects after i.e. heavy rainfall will then be pumped into a treatment system and will no longer end up in rivers untreated. The two identical machines achieved a tunnelling performance of up to 187.5m and 208.5m per week respectively under the former Olympic city.
