A Break through for the MTR South Island Line
Excavation of the 3.2-kilometre Nam Fung Tunnel connecting Admiralty and Ocean Park stations on South Island Line (East) (“SIL(E)”) was successfully completed on 17 October 2014. The breakthrough marks an important step forward in the construction programme for the future rail connection between the Southern District and the business centre on the northern part of Hong Kong Island.
Drill-and-blast excavation works for Nam Fung Tunnel commenced in August 2012 and was undertaken in a single direction from south to north with only one work front. A total of 750 blasts were carried out with 500 tonnes of explosives detonated, producing approximately 280,000 cubic metres of excavated material.
“The construction of Nam Fung Tunnel has been one of the biggest challenges of the SIL(E) project due to the difficult underground conditions along the tunnel alignment. Hundreds of construction workers, engineers and other specialists have strived hard to overcome the challenges with a view to creating the shortest route between the north and south sides of Hong Kong Island for the convenience of the community.
I am most grateful to our contractor partner who has worked closely with the MTR team to complete this challenging work,” said Mr TC Chew, Projects Director of MTR Corporation.
The tunnel excavation works had to pass through Wan Chai Gap Fault Zone and Magazine Gap Fault Zone, where there were soft materials within the rock and a higher chance of water ingress into the tunnel. Additional grouting and tunnel strengthening works were therefore required.
With the excavation carried out in a single direction with only one exit, careful coordination was required to manage the heavy traffic in and out of the tunnel every day to transport the spoil from the blasting while bringing in construction materials for the tunnel structures.
Taking great care to minimise the impact of the excavation works on various stakeholders and the environment, the team implemented robust noise mitigation measures, closely monitored vibrations from blasting and maintained continual communication with the local community.
The contractor also enhanced the environmental measures including setting up an award- winning filtering system that recycles waste water for further use in the works site to conserve water. Moreover, the Corporation has focused on providing workers with a safe and healthy working environment.
“Tunnel excavation is very tough work especially under such difficult geological conditions, so we do our best to make things easier for our workers. In addition to regular checks on air quality and the provision of adequate ventilation facilities, we also offer, for example, air-conditioned rest areas and ice cooling at work fronts to make the working environment more comfortable,” said Mr Chew.
With all tunnel excavation works and about 80 percent of the tunnel lining works for Nam Fung Tunnel completed, track-laying works and installation of trackside cables and overhead lines will commence soon. Meanwhile, the extension works at Admiralty Station, in particular, the underpinning works of the Island Line tunnels, remains the biggest challenge in the SIL(E) project.
The project team will continue to strive to complete the works as quickly as possible. Construction of the South Island Line (East) project began in May 2011. As at the end of September 2014, more than 78 percent of the overall works has been completed.
The line runs 7 kilometres from Admiralty to South Horizons with three intermediate stations at Ocean Park, Wong Chuk Hang and Lei Tung. Comprising tunnel and viaduct sections, the medium capacity railway will operate trains at a frequency of approximately 3 minutes during peak hours.