Breakthrough ahead of schedule in China 21 Jun 2018

In mid-May 2018 the national-record-setting 7.9m (26ft) Robbins main beam TBM at the Jilin Lot 3 water supply tunnel in China broke through. A formal ceremony followed to commemorate the excellent performance of the tunneling operation and its early completion.

Breakthrough nearly five months ahead of schedule

“I have participated in this project from the beginning," said Wu Zhi Yong, Vice Chief Engineer and Jilin Yinsong Project Vice General Manager for contractor Beijing Vibroflotation Engineering Co Ltd (BVEC). "The TBM broke through 147 days earlier than scheduled after achieving the fastest monthly advance rate record of 1,423.5m (4,670ft) for 7m to 8m (23-26ft) diameter TBMs in China. The machine excavated more than 1,000m (3,280ft) per month for three consecutive months.”

The completion of the 24.3km (15 mile) tunnel nearly five months ahead of schedule is a great achievement considering the difficult ground conditions encountered. Rock types ranged from tuff to granite, sandstone, and andesite with multiple fault zones—conditions requiring nearly continuous ground support. Rock strengths varied widely from 35 to 206 MPa UCS (5,100 to 30,000 psi).

Formal ceremony at breakthrough

National record of 1,423.5m in one month

According to Wu, there were a number of factors that contributed to the swift advance rates. “The stable and reliable performance of the Robbins machine, the professional technical skills of the service technicians, the Robbins crew coordination, reasonable working progress arrangements and the sophisticated technology all allowed the project to make the fast advance rate,” he said.

The Robbins main beam TBM bored through a total of 24 fault zones utilizing a combination of steel McNally slats (extruded through pockets in the TBM roof shield to prevent movement of loose rock), wire mesh, and shotcrete. The TBM was designed specifically to tackle the tough conditions. “Under the variable ground conditions, especially weak, soft, and fractured rock, the optimized system and reasonable design of the machine ensured effective tunneling progress," said Wu. "The Robbins gripper system, continuous propel system, hydraulic drives, roof support and stable cutterhead, reduced the wear of cutters. The efficient belt conveyor inside the main beam allowed quick muck removal from the cutterhead to the back of the machine, which ensured the good progress of the TBM,” he added.

The Jilin Lot 3 tunnel is part of the Jilin Yinsong Water Supply Project, which at 736.3km (457.5 miles) is China’s largest scale water diversion project to date. Once operational the water lines will divert water from Fengman Reservoir at the upper reaches of Di’er Songhua River to central regions of Jilin Province which are experiencing chronic water shortages. These regions include the cities of Changchun and Siping, eight surrounding counties, and 26 villages and towns under their jurisdiction. The project will optimize water resource distribution, improve regional eco-systems, and ensure better food production and water safety for the people of Jilin Province.