Tunnelling work on the US$139m MTRC Quarry Bay Congestion Relief Works Contract 680 is scheduled for completion at the end of this month (April). The final 245m section of the 390m westbound overrun tunnel towards Tin Hau Station was due to start as T&T International went to press.
Contractor Nishimatsu opted for TBM drives to excavate the two 6.2m diameter, 1.9km long tunnels. The major tunnelling section of the contract involved two TBM-driven sections diverging east and west of Shaft N, being bored by two Robbins machines. Drill+blast is being used for associated works.
The first of these drives runs east from Shaft N to Quarry Bay Station, breaking through into the existing overrun tunnels on the Kwun Tong Line. Drive lengths are 1.5km on the eastbound section and 1.4km on the westbound.
Excavation started in Dec ’98 and was completed in May ’99. Currently, lining works are complete between North Point and Quarry Bay and approximately 40% complete between Shaft N and North Point.
The second section – from Shaft N to Tin Hau Station – comprises a 397m long eastbound drive and a 390m long westbound drive. The eastbound drive started in late August ’99 and was completed four weeks later. The westbound drive is now under way. TBM mucking out on the completed drives was achieved using horizontal tunnel conveyors and a vertical pocket lift at Shaft N.
The 25m long Robbins TBMs are both 6.2m in diameter and are armed with 40 circular 479mm cutter discs. The bores are reduced to a 5.8m diameter by mass concrete lining with a full circle geotextile and membrane waterproofing system down to a sub-invert slab groundwater collection drainage system.
The first machine, having completed its work on the main section of tunnels, is being refurbished ready for use by Kumagai-Gumi on the New Wu-Chien Diversion Tunnel in Taiwan. Previously, it had been used on the 9.4km long, 5m diameter Lötschberg AlpTransit exploration tunnel in Switzerland. The second TBM, working on the final drive, was previously used on the Nam Fung Road- Mt Parker Hong Kong electric cable tunnel in 1990. Nishimatsu is using Tamrock semi-computerised jumbos and LHD loaders to construct the drill+blast sections, which include a maze of passenger adits and staircases at the new North Point Station. The company is also building a 40m deep plant building to feature seven underground and three above ground levels.
Overall excavation is approximately 60% complete, and lining operations are 40% complete. At Shaft N, all underground crushing operations are handled by a Nordburg NW80 machine.
Related Files
Quarry Bay to Tin Hau Station
