Desiree Willis, Technical Writer, The Robbins Company

25.4km single TBM heading

Spanning 10 years and more than 200km of tunnel, China's Yellow River Water Diversion Project can only be called epic. The latest installment of this extensive scheme, the 25.4km long x 4.8m (15.7ft) diameter Pinglu Tunnel, will be one of the world's longest tunnels excavated with a single TBM. In early July, the Robbins double shield TBM driving the tunnel set ring number 15,000 to mark the heading nearly three quarters complete.

The contracting group Sino-Austria Hydraulic Engineering Co Ltd (SAHEC) is responsible for the Pinglu Tunnel project and has been operating the machine since September 2006, driving through mixed strata of about 50 MPa in UCS. By mid-July, about 7km of the 25.4km long drive were left to excavate by mid-July.

"We've had high output in some very challenging ground conditions," said Paul Bargmann, machinery department head for Alpine Bau GmbH, lead partner in the SAHEC JV. "We've worked in conditions from soil to often sticky, medium hard rock, to highly abrasive sandstone and traces of coal."

The machine broke through into a shaft chamber at the 13km 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.

Intermediate breakthrough

Historical connection

The Robbins machine on the project has been working in China since 2000 when it was used to bore the 12km long Lot 5 tunnel on an earlier section of the Yellow River Diversion. During the course of that drive, the machine set two world records for its 4m-5m (13ft-16ft) diameter class: best month 1,855m (6,085ft) and best monthly average 1,352m (4,435 ft). Both records still stand.

All the TBM-driven tunnels are lined with the precast concrete hexagonal segmental system. The segments for the Pinglu project are produced in the city of Shuozhou about 15km from the jobsite. The segments of the lining system are placed in rings of four elements in a honeycomb configuration staggered longitudinally. The system was designed to allow for high-speed continuous boring with no downtime for erecting segments.

4.8m diameter mixed ground drive

The Pinglu Tunnel will connect to the North Main Line of the Yellow River Project, which includes another 15km of drill+blast tunnels that will transfer water to the Pinglu, Shuozhou, and Datong areas. More than 100km or 62 miles of the South Main Line was excavated between 1999 and 2001 using five TBMs, including four Robbins double shield machines. The entire scheme will transfer water from the Yellow River to regions of Shanxi Province that are chronically dry, receiving only about 400mm or 16in of rainfall per year.

References

Record setting TBMs on Yellow River drives - TunnelTalk , Jan 2001