Ever since construction started on the MTR Shatin to Central Link project, I’ve had one big question – how would the two new lines interface at Hung Hom station, and interface with the new and existing tunnels?
The Sha Tin to Central link (abbreviated SCL; Chinese: 沙中線) consists of two new railway lines:
- Phase 1 from Tai Wai station in the New Territories to Hung Hom station in Kowloon, connecting the Ma On Shan line and West Rail line forming the Tuen Ma line, codenamed “East West Corridor”.
- Phase 2 from Hung Hom station to Admiralty station on Hong Kong Island as an extension of the East Rail line, codenamed the “North South Corridor”.
Four new underground platforms are being built to serve the new railway lines.
These newly built platforms will be clean and bright.
Compared to the dark and dingy platforms used by passengers today.
8-car long trains on the East West Corridor will use the island platform on the top level, with 9-car long trains on the North South Corridor using the island platform below below.
This arrangement allow the North South Corridor to pass under Victoria Harbour via a new immersed tube tunnel.
The new platforms are located next door to the existing platforms at Hung Hom.
Allowing construction to continue without disrupting rail services.
But is a challenging process, in a confined space located beneath the existing station podium.
With deep excavations beneath the station and podium and the close proximity of the works to existing structures, all construction works for SCL 1112 have to be carefully considered in advance and assessed for their potential impact on the integrity and safety of the structures above.
At an overall station depth of approximately 15 m below ground, the deep excavations require ground support. Diaphragm walls are the primary form of ground support and also form the permanent station walls. The diaphragm wall construction technique used provides an effective groundwater cut-off during excavation and offers robust protection to the existing structures.
Another main challenge at Hung Hom is that the headroom available beneath the podium structure is relatively low, making construction works more difficult. Specialised plant and equipment was required to construct these diaphragm walls, excavating the soil down to competent rock. Once the excavation is completed, steel reinforcement cages were installed to give the panel the required strength. Each of these reinforcement cages can only be installed in 4m-long sections due to height restraints beneath the podium, and so a considerable number of these cages had to be joined together to create a single panel. Such works took considerable time and was labour intensive. Once the cages were installed, concrete is placed in the panel and then that panel is complete.
In a number of locations beneath the podium the required SCL alignment conflicts with the maze of existing podium foundation columns. To remove these column’s sophisticated jacking systems are required to transfer the existing podium loads onto new foundation structures, clear of the SCL alignment, before the existing foundations can be removed. The structures, new and old, are monitored 24-hours per day to alert the construction teams of any potential concerns which may affect the safety of the structures.
New tracks will tie the underground platforms to the existing network.
Ground level tracks at the south end connect the upper level East West Corridor platforms to the existing West Rail tunnel towards East Tsim Sha Tsui.
While to the north, more ground level tracks connect the East West Corridor to the new tunnel towards Kai Tak and Tai Wai.
And a new tunnel beneath these tracks takes the North South Corridor north towards Ho Man Tin.
Where they will rejoin the surface tracks.
What about Through Trains?
It appears that the six current above ground platforms will be retained for the use of Intercity Through Trains.
With the Chinese-language Wikipedia entry on Hung Hom station containing this unvalidated theory:
Following the completion of the East Rail Line extension across the Victoria Harbour, the current platforms 1-4 will be converted for use by Intercity Through Trains.
The shunting track for platform 1-4 was dismantled to allow the construction of the East Tsim Sha Tsui extension in 2001, followed by the removal of the connection between platform 2 and the current East Rail Line with the opening of the Kowloon Southern Link in 2009.
The track to these platforms will be reconfigured following the opening of the East West Coridoor, and the locomotive traverser will be modified to be suitable for long-body locomotives such as the HXD1D.
But my theory – two platforms are more than enough to cater for Intercity Through Trains, so no modification works will be carried out – platforms 1 though 4 will instead be sealed off from public access and then abandoned.
And a footnote on stabling sidings
Another Shatin to Central Link project activity at Hung Hom station are the Hung Hom Stabling Sidings, occupying the former Hung Hom Freight Yard, under an existing podium structure.
Thirteen tracks will be provided in the new sidings to permit stabling, cleaning and inspection of trains, with full maintenance facilities located at Pat Heung and Tai Wai depots.