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
In Switzerland a structure of the century is under construction: the Gotthard Base Tunnel. The longest traffic tunnel of the world will be 2 x 57 kilometers long and will turn the connection Basel-Milan into a flat rail link. After its completion, trains can go twice as fast as hitherto. Including all shafts and galleries, a total of 153,5 kilometers have to be excavated through a changeable and challenging geography – with an overburden of up to 2,000 meters and rock temperature up to 50° C. One of the most critical challenges was the Piora Basin situated on the southern section between Faido and Sedrun. For this fault zone, with a length of about 150 meters, the tunnel workers had to take into account to encounter non stable rock, possibly under high water pressure. For the mechanized tunnelling of the two main tubes under the St. Gotthard only Gripper TBMs made by Herrenknecht are operation and will excavate about 85 kilometers of the new railway tunnel.
The south: Bodio - Faido – Sedrun.
In autumn 2006 the successful completion of the southern section from Bodio to Faido was celebrated. The TBMs S-210 (“Sissi”) and S-211 (“Heidi”) entered the multifunction station at Faido on September 6, and October 26, 2006. Following the subsequent comprehensive revision, the diameter of both machines was increased from 8,830mm to 9,430mm in order to tackle the adjacent section towards north: from Faido to Sedrun. Both hard rock machines coped with the Piora Basin in October 2008 and February 2009. On October 15, 2010 the final breakthrough was celebrated in the Eastern tube followed by the final breakthrough in the Western tube on March 23, 2011. The "Era Gotthard" is finished successfully. The deviation from the set point amounted to a mere 3 millimeters vertically, horizontally an absolute precision landing was achieved: 0 millimeters deviation.
The north: Erstfeld - Amsteg - Sedrun.
The two Gripper TBMs S-229 (“Gabi 1”) and S-230 (“Gabi 2”) completed the section Amsteg – Sedrun in the north of the Gotthard massif in June and October 2006. They were dismantled inside the mountain and refurbished comprehensively. After that they were restarted at the Erstfeld portal, the nothernmost point of the Gotthard Base Tunnel, for the advance of the track Erstfeld – Amsteg. On June 16, 2009, a big celebration was held on the occasion of the breakthough of “Gabi 1” in Amsteg . The sister machine “Gabi 2” in the parallel tunnel finished very strong. On July 19, a top performance of 56 meters of new tunnel within 24 hours was achieved. Precisely 3 months after "Gabi 1" celebrated breakthrough on September 16, 2009.
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.
