The 11.8 km Route 3 Country Park Section
expressway is divided into four major distinctive sections: Ting Kau Bridge
and the approach viaduct, the road section leading to the southern entrance
of Tai Lam Tunnel, the Tai Lam Tunnel, and the approach road and interchange
system at the northern end of the tunnel. This is the most complex highway
and tunnel system in Hong Kong.
The 880-metre waterway
of the Rambler Channel, which separates the Tsing Yi Island and Ting Kau,
is now connected by a cable-stayed bridge which is supported by three
independent towers. The foundation of the towers is composed of large-diameter
bored piles, anchored to provide better stability in resisting wind. The
structure of the towers was constructed in slipforms with the use of 65
mpa high-strength concrete.
Between Ting Kau
Bridge and Tuen Mun Highway there is a 510 m approach viaduct that spans
Castle Peak Road and Tuen Mun Highway before it reaches the road sections
leading to the southern entrance of Tai Lam Tunnel. This approach viaduct
was constructed of box-section, cast-in situ concrete by a balanced cantilever
method with the use of a traveler formwork system. A slip road made of
precast concrete beams supported on high level piers and portals leads
traffic from Tuen Mun Highway to Tai Lam Tunnel.
The 3.8 km Tai
Lam Tunnel consists of three tubes. Two tubes handle three lanes of traffic
each, while the smaller diameter middle tube is a servicing duct for ventilation
and maintenance purposes. The Tai Lam Tunnel was excavated using the drill-and-blast
method. The contractor employed a series of computer-operated drilling
rigs so that the drilling pattern could be accurately calculated. The
drill holes were then filled with emulsion compound and gassing agent
to produce the necessary explosion. The crushed rock was excavated and
transported to the exit of tunnel by conveyor belt for disposal. The progress
of excavation was about 5 m per day at the peak. As soon as the excavation
was completed, a concrete lining was formed by the use of a large mechanical
form system so as to strengthen and seal the exposed rock surface permanently.
The tunnel excavation
started simultaneously at both north and south ends. The works at the
south and north ends were carried out by Dragages and Nishimatsu, respectively.
Unlike other tunnel designs, there is a ventilation building on both ends
of the Tai Lam Tunnel. This building is so designed that it also serves
as the entrance to the Tunnel.
There is a 6.2
km approach road leading traffic from the northern end of the Tai Lam
Tunnel to Au Tau through Kam Tin area. In addition to the construction
of the approach road, this part of the project also included the construction
of the toll square and the administration building for the tunnel joint-venture
consortium, as well as a slip road and interchange system leading to Yuen
Long Bypass and Kam Tin Road.
As for the construction
of the approach road, there were several major rock cuts between Shek
Wu Tong and Ko Po. Difficulties encountered in this part of work were
mainly due to the scale of rock cutting as well as some major fractures
in the cut rock requiring further stabilisation using anchor systems.
Route 3 Contractors Consortium
Nishimatsu Construction Co Ltd/Dragages et Travaux Publics (HK) Ltd