Construction Methods for Tunnel

8/12/2019 Construction Methods for Tunnel

1/11

Construction Methods for TunnelConstruction Methods for Tunnel

I) Drill and Blast

II) Immersed Tube

III) Tunnel Boring Machine (TBM)

IV) Cut and Cover


2/11

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


3/11

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


4/11

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


8/11

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


9/11

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


10/11

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


11/11

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

Documents

Construction Methods for Tunnel