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Switzerland, Zurich-Thalwil - ch/13


To be driven in opposite directions from two shafts by 12.3 m-diameter Herrenknecht TBMs: one a hard rock, the other a dual-mode Mixshield slurry machine. First machine launched at Allmend Brunau shaft towards Thalwil, Sept 1998. 9.4 km long to connect with proposed Gotthard AlpTransit tunnel at Nidelbad. Contracting jv of Prader, Locher, Wayss & Freytag. Nov 1998.   Two TBMs now at work, with 12.29 m-diameter south drive machine 3 km into its 5.6 km drive having recorded a best day of 39.1 m or 23 rings while completing 673.2 m of tunnel in June, 1999. First 330 m of north drive being undertaken by second TBM in rock mode using disc cutters and conveyor belt. Following 150 m will be in slurry mode using hydraulic spoil pipelines to surface separation plant. Machine will then complete the bulk of the 2.7 km drive in rock mode in molasse. The final 700 m will be in soft mixed ground with extra drag picks on the cutterhead. Lining comprises seven bolted segments and key, 12.04 m outside diameter and 11.44 m internal diameter. Aliva pumps are used at both TBMs to pump pea gravel into the annulus. Segments are transported by converted Kiruna trucks. There are vehicle turntables behind each TBM. Zimmerberg will connect with AlpTransit Gotthard in a continuous tunnel, possibly using the same machines. Sept 1999.   South section TBM driving 5.6 km from Allmend Brunau to Nidelbad in typical Sweetwater molasse has passed the halfway point and completed 673.2 m in June, 1999 with a best day of 39.1 m or 23 rings. Conveyor capacity is 1,100 t/h using 1 m-wide belt at 2.2 m/sec. Major constraint is the rate at which spoil can be removed from site because only 13 trains/day can be handled. However, 100,000 t surface stockpile will smooth rockflow. First 330 m of 2.7 km north drive was in hard rock, then TBM was converted to slurry mode for 150 m following which it will revert to hardrock configuration. Visit www.herrenknecht.com November 1999.  Rail 2000 Thalwil junction and 900m/1,300m branch tunnels completed using drill/blast to connect with advancing cut and cover. TBM face in main tunnel left ready for AlpTransit drive to Nidelbad when finances are available. Herrenknecht TBMs completed drives in both directions from Allmend Brunau shafts and removed for storage. 27/02.