15,000th Ring Marks Milestone for Robbins Double Shield

Sep 15, 2009

Long-distance TBM nears completion of China's Pinglu Tunnel: Spanning over 10 years and 200 km (124 mi) of tunnel, China’s Yellow River Water Diversion Project can only be called epic. The latest installment of the extensive scheme, known as the Pinglu Tunnel, will be one of the world’s longest tunnels excavated with a single TBM. On July 9, 2009, the 4.8 m (15.7 ft) diameter Robbins Double Shield TBM boring the waterway set ring no. 15,000, making the tunnel nearly three quarters complete.

The Sino-Austria Hydraulic Engineering Co. Ltd (SAHEC) is responsible for the 25.4 km (15.8 mi) tunnel, of which about 7 km (4 mi) were left to excavate in mid-July 2009. The machine has been boring since September 30, 2006 in mixed strata up to 50 MPa UCS. "We’ve had high output in some very challenging ground conditions, from soil to often sticky, medium hard rock, to highly abrasive sandstone and traces of coal,” said Paul Bargmann, machinery dept. head for Alpine Bau GmbH, lead partner in the SAHEC JV. The machine broke through into a shaft chamber at the 13 km (8 mi) halfway point in October 2008, and was refurbished before starting up again in December. The final breakthrough is scheduled for the end of April 2010.
The Robbins machine has been operating in China since 2000, when it was used to bore the 12 km (7 mi) long Lot 5 tunnel on an earlier section of the Yellow River Diversion. During the course of excavation, the machine set two world records in its size class of 4 to 5 m (13 to 16 ft): best month (1,855 m/ 6,085 ft) and monthly average (1,352 m/ 4,435 ft). Both records still stand.
Lining for all of the TBM-driven tunnels has consisted of unique hexagonal segments, produced in the city of Shuozhou about 15 km (9 mi) from the Pinglu jobsite. Segments are placed in rings of four elements, in a honeycomb configuration staggered longitudinally. The design was created to allow for high-speed, continuous boring with no downtime while erecting segments.
The Pinglu Tunnel will connect to the North Main Line of the Yellow River Project, which additionally includes about 15 km (9 mi) of drill and blast tunnels that will transfer water to Pinglu, Shuozhou, and Datong areas. Over 100 km (62 mi) of the South Main Line were excavated by five TBMs, including four Robbins Double Shields, between 1999 and 2001. The entire scheme will transfer water from the Yellow River to chronically dry regions of Shanxi Province, an area that only receives about 400 mm (16 in) of rainfall per year.

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