construction methods for tunnel
TRANSCRIPT
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Construction Methods for TunnelConstruction Methods for Tunnel
I) Drill and Blast
II) Immersed Tube
III) Tunnel Boring Machine (TBM)
IV) Cut and Cover
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Existing Road Tunnels in Hong Kong
Drill and BlastDual-10.9Discovery Bay Tunnel
Construction MethodNo. of CarriagewaysTunnel Length (km)
Drill and BlastDual-31.25Nam Wan Tunnel
Drill and BlastDual-33.8Tai Lam Tunnel
Drill and BlastDual-31.6Cheung Tsing Tunnel
Immersed Tube + Cut and CoverDual-32Western Harbour Tunnel
Drill and BlastDual-24Tates Cairn Tunnel
Drill and BlastDual-20.9Tseung Kwan O Tunnel
Drill and BlastDual-22.6Shing Mun Tunnel
Immersed TubeDual-32.2Eastern Harbour Crossing
Cut and CoverDual-21.3Airport Tunnel
Drill and BlastDual-21.9Aberdeen Tunnel
Immersed TubeDual-21.9Cross Harbour Tunnel
Drill and BlastDual-21.4Lion Rock Tunnel
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I) Tunnel by Drill and Blast Method
Required the tunnel to be found in
competent rock with Grade III or better;
Geological conditions, Grade III rock maybe very deep below ground levels
Detailed GI
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II) Tunnel by Immersed Tube Method
Considering the characteristics of marine mud, immersed tubetunnel is expected to be found on alluvium, for the following
reasons:
The top of the partially dredged mud would be heavily disturbed
and softened to different degrees along the alignment.Subsequent placing of the tunnel box would cause unevensettlement at the different units.
Extremely difficult to achieve a good blanket before placing the
tunnel units, leading to permeation of clay and henceuncontrolled settlement.
Inadequate bearing capacity from the marine mud duringconstruction when the tunnel units have to be temporarily
supported by foundation.
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Tunnel Boring Machine (TBM)
The Worlds Largest TBM
(15.2m diameter) is
required, which is being
adopted by Shanghai
Chongming South
Channel Tunnel (target
completion by 2007).
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Tunnel Boring Machine (TBM)
Uncertainties with regard to construction practicability of
applying the giant TBM;
Difficult handling and logistics of such huge TBM;
A very large working area (approximately 5 ha) for the assemblyand operation of equipment
Substantial and extensive ground treatment in the areas of
cavities and fault zones;
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Tunnel by Tunnel Boring Machine (TBM)
Restriction:
Impacts such as water quality and ecology
Waste generated
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Cost and Programme Comparison
with Viaduct OptionReference Projects:
1. Groene Hart Tunnel Netherlands:
tunnel length ~7.1km tunnel external diameter = 14.87m
no reclamation contract period ~4.5yrs, target completion by early 2005 contract sum ~HK$ 4,300M
2. Chongming South Channel Tunnel Shanghai:
tunnel length ~8.9km tunnel external diameter = 15.2m
contract period ~4yrs, target completion by 2007 contract sum ~HK$ 11,500M
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Tunnel tunnel length ~3.9km tunnel external diameter = 15.2m
need reclamation estimated programme ~(4.5/7*5 = 3.2yrs) + ~1.5yrs for
reclamation (require the artificial island completed first forworks area), therefore total ~4.7yrs
estimated cost ~11500/8.9*3.9 = HKD 5,050M
For viaduct option(reference to Shenzhen Western Corridor,
3.3km, 2.5yrs, HKD 2,200M): length of viaduct ~3.9km estimated programme ~3yrs estimated cost ~HKD 2,600M
Cost and Programme Comparison
with Viaduct Option
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General Issue related to Tunnel
Restriction:
Restriction to dangerous goods vehicles Cat 1, 2 and 5;
Traffic speed of tunnel to be limited to 80km/h;
Connectivity
No lane changing
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8914,059Viaduct over sea
(referenced to Shenzhen
Western Corridor)
51418,166Drill and Blast Tunnel
(including E&M works)
(referenced to Nam Wan
Tunnel)
Annual Recurrent Cost
(HK$/m2)
Construction Capital
Cost (HK$/m2)
Cost Comparison between Tunnel and Marine Viaduct