Page 9 - TunnelTalk Annual Review 2011

Hong Kong express
to mainland China
Route to West Kowloon Terminus
One of the largest tunnelling challenges ever for Hong Kong has been getting underway on site with preparatory works to mark commencement of the high-speed Express Rail Link (XRL).
The project, with an almost 26km underground alignment, will extend from Hong Kong to the border with mainland China as part of a larger high-speed scheme that will join the new railway to the growing cities of Shenzhen and Guangzhou.
The large transport scheme will further tighten the economic and social bonds along this thriving axis, and tie-in to China’s national rail network beyond Guangdong Province.
MTR Corporation is developing the XRL project on the Hong Kong side of the border. The dedicated, entirely underground corridor was given over to the strategic transport link approved by the Hong Kong Government to proceed towards completion by 2015.
Within Hong Kong, the underground route from central Kowloon to the border, is split into a chain of contract packages on which a variety of tunnelling methods are to be employed. Evacuation is predominantly drill+blast for single tube stretches, with twin tube TBM sections, and some cut- and-cover excavation.
XRL tunnels
For XRL, the Hong Kong section requires about 51.4km of main line tunnelling, to run through hills, beneath villages, and under the Shenzhen River.
In plan, the route is formed by two S-curves, the first on a relatively tight alignment out of downtown Kowloon for about 40% of the line, and the second on a more relaxed route up through the New Territories to the border into Shenzhen.
The rail line passes below a low mountain range as the tight S-curve transits into the second S-curve with two other areas of high cover being short ranges of hills on either side. Maximum cover on the alignment is up to a little more than 600m with the low, flat elevations in built-up areas ranging between 5m-55m below ground surface.
Geology along the alignment comprises varied rock strata, including volcanics and granites,aswellassoftandmixedground conditions.
The tunnels will be of varying internal diameter. The twin tube TBM sections range between 8.15m and 8.7m i.d. and are linked by cross passages, whereas stretches of single-tube, double-track drill+blast excavation are about 15m wide. From the total tunnelling required, there will be approximately 14km of drill+blast, 17km (2 x 8.5km) of parallel TBM bores, 4km (2 x 2km) of cut-and-cover, and 2.4km (2 x 1.2km) of cut-and-cover for works near the terminus at West Kowloon.
Along the alignment there will be eight ventilation buildings and emergency access points, and at Shek Kong there will be an emergency rescue station (ERS) and stabling sidings (SSS) on a 2km long x 150m wide corridor.
Patrick Reynolds, TunnelTalk Procurement
Following approval by the Executive Council of Hong Kong’s Government in October 2009, procurement was quickly underway with a staggered programme of bids and awards for nine principal underground packages. Calls for pre-qualification were issued in the second and third quarters of 2009 and awards of contracts were spread through 2010.
While preparatory works began in early 2010, notices to proceed on the large lump- sum contracts for the main underground works were issued up to late 2010 (Table 1) with main excavation starting in 2011.
Tunnelling schedule:
Commencing 2011
C811A
Bachy Soletanche-Laing O’Rourke JV cut- and-cover works for the south approach tunnel at the terminus involve construction of a 270m long tunnel to run below the existing Kowloon Southern Link tunnel. This includes a 170m long piled section.
C811B
Gammon-Leighton JV for the north tunnel will excavate 430m of cut-and-cover piled tunnel.
C822
Leighton Contractors (Asia) will excavate a 7.7km long, single tube, drill+blast tunnel plus a 2.5km long ventilation tube, a 120m
www.TunnelTalk.com TunnelTalk AnnuAl Review 2011
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Images courtesy of MTR Corporation
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