The Dahuofang Water Tunnel is a large reservoir diversion project that will transport water from high rainfall areas to the dry, heavily industrialized Shenyang region of China. The total length of the tunnel is 85.3 km (53 mi) with over 60 km (37 mi) being driven by tunnel boring machines (TBM) — one of the world’s longest TBM-driven tunnels.
The project owners awarded construction contracts in three lots, each about 20 km (12 mi) long. Lot 1, awarded to Beijing Vibroflotation Engineering Co Ltd, chose an 8.03 m (26.3 ft) diameter Robbins Main Beam TBM for the project. The machine is responsible for a 20 km (12 mi) bore in migmatite and orthopyre geology.
The Lot 3 contract was awarded to The Bureau of Water Conservancy and Hydroelectric Power Construction, who chose a nearly identical 8.03 m (26.3 ft) diameter Robbins Main Beam TBM for a 16 km (10 mi) long bore. This section of tunnel also passes through migmatite geology, but about two-thirds of the tunnel contains a complex mixture of heavily weathered and fractured rock.
Both Robbins Machines include forty-three 19 in (483 mm) cutters and eight 17 in (432 mm) center cutters. The cutters are backloading with frontloading optional. Both machines use variable frequency drive systems and can generate a maximum thrust of 22,934 kN (5,155,767 lb) and the cutterheads of both machines have a torque of up to 6,275,000 N-m (4,628,202 lb-ft).
Robbins also provided the back-up systems for both machines. Each back-up includes a bridge conveyor, transfer conveyor, track-laying area, and rolling gantries among its units. The TBMs use slightly different conveyor systems — the conveyor for TBM 3 is a shorter length with a consequently reduced power-drive system.
The TBM accessory equipment mounts included probe drills and rock bolting systems, which are compact for working in limited space.
The Robbins TBMs began boring in June and July of 2005. In March of 2006, after only 8 months of boring, TBMs 1 and 3 had advanced 3.8 and 4.0 km (2.4 and 2.5 mi), respectively. The TBMs completed tunneling in 2007.