Work on the 24.3km long Jilin Lot 3 tunnel water conservation tunnel for Jilin Province Water Investment Group has set a new record for 8m diameter bores in China after advancing more than 1,400m in one month.
The record was set by a Robbins Hard Rock Main Beam tunnel boring machine (TBM) is being used by contract Beijing Vibroflotation Engineering Co on the scheme.
The world record is still held by the Tunnel and Reservoir Plan project in Chicago, US which drove 1,482m in one month and was set more than 20 years ago.
Tunnel boring machine Robbins Jilin
On the Jilin scheme, 14km of the tunnel has now been completed with an average monthly advance rate of 708m a month since the TBM’s launch in March 2015. According to the contractor, this is three times faster than would be possible with conventional drill and blast techniques.
Ground conditions on the project are challenging with rock strengths varying from 35MPa to 206MPa with tuff, granite, sandstone and andesite expected and up to 24 fault zones on the route.
Robbins has said that the TBM was designed for the expected ground conditions and is equipped with four rock drills, McNally pockets in the roof shield for the ability to install McNally slats, a ring beam erector, and a shotcrete system. The McNally slats were used in difficult ground encountered in the tunnel.
The Jilin Lot 3 tunnel is part of the Jilin Yinsong Water Supply Project, which will convey water to the central cities of Jilin Province. The total length of the supply line is 263.5km.
Tunnelling is expected to be completed late this year.