Contract 901 was a highly complex project to expand the existing Admiralty Station into a four-line interchange, integrating the existing Island Line and Tsuen Wan Line with the South Island Line and the future Shatin to Central Link. In December 2016, MTR Corporation’s South Island Line completed construction and began operations, providing additional public transport options from the Southern District of Hong Kong Island to the existing MTR network at Admiralty Station. The expectation is this new line will transport approximately 170 000 passengers per day.
Contract 901 works delivered an extension to the existing Admiralty station, providing a convenient interchange between the existing network and the new interchange concourse and four new platforms; two for the SIL (E), and two for the future Shatin-to-Central Link. A large-span cavern and two platform tunnels were excavated immediately below the existing Island Line platform, which was successfully underpinned while continually running trains safely above.Aurecon provided geotechnical, civil and tunnel engineering services for Contractor Kier-Laing O’Rourke-Kaden Joint Venture.
The site was in the heart of Hong Kong Island. The high-density built environment presented numerous constraints and challenges from surrounding high-rise buildings, major roads, and significant underground infrastructure.
A key aspect of the project was interfacing with the operating railway at one of MTR Corporation’s busiest interchange stations. Underpinning the existing SIL finger platform was a highly complex task that required innovative engineering. Both Admiralty Station and the Island Line remained fully operational during the entire construction period.The new station cavern has a large excavated span, is situated underneath a major traffic corridor carrying east-west traffic across Hong Kong Island, has relatively low rock cover, and is near the foundations of a high-rise development.
Aurecon carried out the detailed design of rock support for caverns, tunnels, adits and station box including Island Line underpinning, as well as elements of the permanent concrete lining in the cavern and platform tunnels. Aurecon also undertook the blasting assessment reports for drill and blast excavation.
Understanding the in-situ ground conditions and controlling ground movement were vital. Aurecon developed a comprehensive and robust multi-staged methodology for design of the temporary ground support with state-of-the-art numerical modelling. The design successfully considered the impact of construction on several structures near the excavation, and loads from existing building foundations.
An innovative excavation and support sequence was developed for the underpinning which provided enhanced stability while reducing temporary support requirements and minimising risk. It included a flexible system of rock support that accommodated construction sequence constraints and optimised as-found ground conditions, thereby significantly improving excavation rates.
Excavation and support of the large-span cavern in a dense urban area posed unique challenges. Despite the scale and complexity of the works there was zero disruption to existing rail services and no impact on the safety of the Tsuen Wan Line or Island Line train service throughout the entire construction period.
This was explicitly a result of the remarkable levels of collaboration between all the parties involved, with innovative design, excellent construction supervision, rigorous planning and attention to detail on work permits and safety procedures. The safe completion of the work marks an outstanding achievement in finalising work to customer satisfaction, maintaining railway performance, and operating in the safest possible environment.
The HK$16.5 billion line, operated with driverless three-carriage trains, will run from South Horizons in Ap Lei Chau to Admiralty via the other three new stations at Lei Tung, Wong Chuk Hang and Ocean Park.
With the new railway line, passengers can travel from South Horizons to Admiralty in approximately nine minutes, as compared with the 25 to 45 minutes taken by using road transport during rush hours.