Construction /

Construction Methods

Since the SCL traverses the developed urban areas across the territory, most of the tunnels and stations will be constructed underground. The construction works include excavation of rail tunnels, pedestrian subways and underground stations (Kai Tak Station, Sung Wong Toi Station, To Kwa Wan Station and Exhibition Centre Station) as well as the extension of existing Hung Hom and Diamond Hill Stations and stabling sidings, viaducts and an elevated station (Hin Keng Station). The construction method (Drill and Blast method, Cut and Cover method, Tunnel Boring or Immersed Tube Tunnel) to be adopted will depend on various factors, such as topography and geology, etc.

Move your cursor over different colour sections to view more details of the construction methods.

Safety is of upmost concern of the Corporation. All construction procedures are planned in details and are being carried out in a prudent manner. Our project teams will closely monitor all construction works to ensure safety during construction. To learn more about our monitoring works, please Click Here

Tunnel Boring Machines

6 tunnel boring machines (TBMs) will be used to construct the tunnels for SCL project; 4 are for Kowloon and 2 are for works on Hong Kong Island. One of the TBMs for tunnels between Diamond Hill Station and Kai Tak Development Area is refabricated in Hong Kong, which is the first in ten years for railway projects.

Sections using tunnel boring machines Total Boring Distance
Ma Chai Hang Playground < - > Diamond Hill Station 3.4km approx.
Diamond Hill < - > Kai Tai Development Area 1.5km approx.
Sung Wong Toi Station < - > Ho Man Tin Station 3.2km approx.
Police Officers' Club < - > Exhibition Centre Station 1.2km approx.
Convention Avenue < - > Admiralty Station 0.9km approx.

How do TBMs work?

With a large rotating steel cutter head at the front of the shield, TBMs can pass through different types of soil, rock or mixture of both. The TBM is a multi-functional construction tool, which can excavate and remove excavated materials, and at the same time install the reinforced concrete lining of the tunnel as it progresses. This method, unlike cut and cover excavation works, does not require disruption to the road surface during construction.

Rotating steel cutter head of TBM

Tunnel breakthrough by Mu Gui-ying

TBM works like a small factory which can accomplish all tunnel construction works in one go with high efficiency.

During the design stage of tunnel construction, the tunnels will be divided into different sections. At each section, there will be a launching shaft at the starting point and usually a retrieval shaft at the destination. The depth of the shafts depends on the rail level of the tunnel alignment. Different parts of component of TBM will be delivered to the launching shaft for assembly. After the completion of rail tunnels, the TBM will be dissembled in the retrieval shaft and transported away.

What are the benefits of TBMs?

Minimise impact on the environment and the neighbouring community
The TBMs work underground, which effectively reduce noise, dust, vibration and disruption, as well as significantly minimises the impact on the community and traffic.

Reduce the risk of settlement and enhance project efficiency
With different work procedures taking place at the same time including excavation and installation of permanent pre-cast tunnel walls, TBM is highly efficient compared with traditional blasting or Cut and Cover tunnelling, hence enhancing project efficiency. Risk of settlement will be greatly reduced and loss or movement of the underground water table will be avoided, minimising impact on the building structure.

Do you know our names?

According to tunnelling tradition worldwide, a TBM is given a lady's name before work commencement as a sign of good luck for the project ahead. The MTR Corporation organised the "SCL TBM Naming Competition" in 2014. Over 7,000 secondary and primary students submitted more than 30,000 entries. For more details, please Click Here

Prize presentation ceremony on 27 June 2014

Say cheers with Princess Wencheng before her journey starts

Want to learn more?

  1. Video for Tunnel Boring - Tunnel Boring Machine (In Cantonese only)

  2. TBM know it all
    (Chinese version)

  3. Leaflet about TBM

Drill and Blast

For underground tunnel sections in rock, excavation is undertaken using the drill and blast method; those include:

  • Tunnel between Hin Keng and Ma Chai Hang Playground
  • Overrun tunnel from the south of Admiralty Station

The drill and blast method is a proven and commonly used rock tunneling method worldwide and in Hong Kong, such as the construction of several underground stations including Quarry Bay, Tai Koo, Fortress Hill and North Point Stations on the Island Line.

MTR Corporation is very experienced in this form of construction for building railways in Hong Kong. Detailed assessments are carried out along the route before blasting. Monitoring points will also be installed to determine any possible impacts on adjacent building structures and ensure the public safety.

  • 1. Drill holes in tunnel surface and install explosives.
  • 2. Detonate the explosive.
  • 3. Remove spoil from tunnel.
  • 4. Install support to the tunnel and prepare for the next blast.

The use of explosives is governed by the Dangerous Goods Ordinance and subject to the stringent control by the Mines Division of Civil Engineering and Development Department (CEDD), the Fire Services Department and the Hong Kong Police Force. Suitably qualified professionals will be employed for the blasting operations and a set of stringent control measures in accordance with the Buildings Ordinance and relevant statutory requirements will be implemented.

Blasting works between Hing Keng and Ma Chai Hang

Noise enclosure on top of a ventilation shaft is built to minimise the noise generated from the underground tunneling works deep down

Blasting works inside the tunnel will be enclosed by blasting doors

Signage is erected on site to notify the public about the blasting schedule

What are the benefits of drill and blast?

Minimise impacts on the neighbouring community
The construction of drill and blast occupies less works surface. Comparing with traditional mechanical operations, drill and blast is more effective as less working period is required. Temporary vibrations and noise may be felt by nearby residents, yet they are minor and occasional in comparison with heavy mechanical excavation. To ensure safety, temporary traffic arrangements may be necessary on nearby roads.

Want to learn more?

  1. Drill and Blast Method Procedure
    (In Cantonese only,
    with English subtitle)

  2. Video for Blasting Works
    (In Cantonese only,
    with English subtitle)

  3.  Drill & blast know it all
     (Chinese version only)

Cut and Cover

For shallow excavation in soft ground, cut and cover method is used. All SCL stations (except Hin Keng Station) and some tunnel sections will be constructed by cut and cover method:

  • Tunnels connecting to Kai Tak Station;
  • Tunnels connecting to Hung Hom Station;
  • Tunnels between Fleming Road and Expo Drive.
  • 1. Sheet piles / diaphragm wall / pipe pile walls are installed to support the excavation.
  • 2. While the excavation continues to the bottom of the tunnel, temporary road decks are placed on the existing road surface to ensure smooth vehicular and pedestrian traffic flow.
  • 3. Construction of station concourse and platforms continues underneath the temporary road decks.
  • 4. The road surface is reinstated after construction of the station concourse and platform is completed.

Want to learn more?

  1.  Cut and cover know it all
     (Chinese version only)

What is diaphragm or pile wall?

Diaphragm or pile walls are commonly used in station and tunnel construction. They are installed to support the neighbouring structure or buildings during construction of underground station or tunnel to ensure the safety.

Machinery Hunt

Heavy machinery will be used to construct diaphragm or pile walls. Let's do a machinery hunt and see what they are good at!

A trench cutter is used to excavate soil and rock in underground stratum to build trench for the diaphragm walls. The trench will be filled with a thick mixture of bentonite during excavations to support walls.

A desander is used to filter and desand the bentonite extracted during excavation.

The bentonite will be stored in silo tanks and re-used.

A piling machine can drive piles underground, supporting the structure of underground stations or tunnels.

What are the benefits to construct underground stations with diaphragm or pile walls?

Diaphragm or pile wall construction enhances the strength of the station or tunnel structure and the safety of buildings in the area. It is a safe and efficient construction method which is suitable for building stations or tunnels in densely populated areas like Ma Tau Wai Road and Wan Chai North.

Works area on Ma Tau Wai Road

Works area at Wan Chai North

Immersed Tube Tunnel

The cross-harbour section of the SCL is 1.7-kilometre long, and is mainly constructed by Immersed Tube Tunnel method. It is formed by 11 pre-cast units, each of around 160-metre long.

Construction sequence:

1.At the same time the IMT pre-cast units are being constructed at the casting yard, a trench is being dredged in the seabed of Victoria Harbour. 2.When the pre-cast unit is completed, it will be towed to Tseung Kwan O for installation of surveying tower and floating pontoons.
3.After fitting-out, each IMT unit will be towed to Victoria Harbour to be lowered into the prepared trench and connect with the other IMT units. 4.Backfill to cover the tunnel and to reinstate the seabed.

IMT casting yard

A casting yard for the construction of immersed tube tunnel units is being set up at the former Shek O Quarry, which was also the casting yard for the Western Harbour Crossing and the Airport Railway cross-harbour section tunnel.

What are the benefits to use immersed tube tunnel?

Higher flexibility and efficiency
While tunnel elements are being fabricated in the casting yard, dredging is being carried out in the seabed of Victoria Harbour concurrently, resulting in higher efficiency;
More direct connection
Tunnel units are not necessary to be laid deep into the seabed which minimises the height difference with the existing railway and provides more direct connection;
Energy saving
Archimedes' principle and contemporary technology of GPS are adopted for sinking the tunnel units, huge machineries are not required;
Minimising impacts on the community
Most of the construction procedures are being carried out in the casting yard away from the urban areas, and the working area within Victoria Harbour is relatively small, causing the least impact on the public.

Want to learn more?

  1. Animation about IMT

  2.  Immersed Tube Tunnel know it all
     (Chinese version only)

  3. Leaflet about IMT construction