Robbins TBMs for 40km China drives

A huge 85.32km long water supply tunnel project in China has selected two Robbins TBMs for 8.03m diameter drives totaling 39.35km of tunnel.

The Dahuofang Reservoir Water Diversion Project is situated to the east of Shenyang City in Liaoning Province and aims to address an already chronic water shortage compounded by a large and growing population. The client, Liaoning Runzhong Water Supply Co. Ltd. used the China International Tendering Company as buyer for the machines with the tender awarded in late 2003. Financed by the Chinese government, the value of Robbins contract for two TBMs is US$33.3M.

Construction got underway on the site in February last year and the first TBM has been assembled onsite. It was due to be moved into the starter tunnel as T&TI went to press and should have begun boring its 20.75km long drive in early June. The second Robbins TBM should follow a similar pattern approximately three weeks later to commence its 18.6km long drive.

The TBMs will be open main beam gripper type TBMs for hard rock. Tunnel support will be by shotcrete with ring beams and mesh if required. The final lining is reinforced concrete.

A representative from Robbins told T&TI how roughly 60km of the 85km long single bore tunnel will be by TBM under three contracts with the balance being excavated by drill and blast. The first TBM will be used by contractor Beijing Vibroflotation Engineering Co. Ltd. (BVEC)and launched from a portal. The other will be operated by the Bureau of Water Conservatory and Hydroelectric Power Construction of Liaoning Province (LWCB) and launched from an underground chamber along the tunnel alignment, accessed by adit. A third stretch of TBM excavated tunnel will be excavated by a Wirth machine and will also be launched from an underground chamber. The final length of the main conveyance tunnel will be excavated by drill and blast, plus there are 16 drill and blast adits intersecting the tunnel alignment.

Tunnel mucking will be by continuously advancing belt conveyor. Due to the long lengths of tunnel involved, the Robbins representative told T&TI that after roughly 10km, each TBM will intersect an adit where the belt will be dismantled and reconfigured to discharge via the adit rather than along he entire length of previously mined tunnel. The construction is due to be completed by 2009.