Breakthrough on two of the drives on West Rail’s Kwai Tsing tunnels in Hong Kong was expected as T&TI went to press.
Firstly, the 1.7km long Ha Kwai Chung single drive twin-track tunnel, being constructed by drill + blast, was slated for breakthrough in mid-October whileHong Kong’s first EPBM is scheduled to breakthrough on the 1.8km long uptrack drive of the twin bore Tsing Tsuen tunnel at the middle of this month.
On completion, the 8.6m diameter NFM machine will then be turned and prepared to start boring on the downtrack tunnel in early 2001 with a seven month completion schedule.
The $246.7M Kwai Tsing contract DB-320 consists of two main tunnels both being constructed by the Dragages/Zen Pacific JV. Firstly the 1.8km long, 8.4m diameter Tsing Tsuen Tunnel is a twin bore, single track TBM drive while the 1.7km long, 13m wide, 9m high Ha Kwan Chung tunnel is being constructed by drill + blast. A 0.12km long cut and cover section will complete the 3.6km section from Mei Foo to Tsuen Wan West.
Drill + blast of the Ha Kwai Chung tunnel in a heavily populated area has enforced the use of extensive noise barriers and covers. This is to ensure adhesion to the stringent requirements imposed by the Environmental Protection Department of SAR government. Due to the proximity of the south portal to Ching Cheung Trunk Road, the Mines Department has also imposed regulations on the blasting works including noise and vibration control.
On the TBM drive the machine has just passed into the final zone of mix soil layers, believed to be the most challenging tunnel section. A West Rail spokeswoman said: "Due to the previous experience of the contractor using the TBM, the operators are competent to solve the technical problems encountered and maintain the progress as scheduled."
