Vol 22 No 5 (04-2013)
MTR Kwun Tong Line Extension -- A 2.6 km long tunnel operated entirely underground


Background

The current railway network has not covered some densely populated areas such as Ho Man Tin, Hung Hom and Whampoa. Meanwhile, the frequent traffic jam from the Cross Harbour Tunnel during peak hours caused great inconvenience to commuters. Therefore, the MTR Corporation (MTR) has long been planning to launch the Kwun Tong Line Extension project (KTE) to alleviate the serious traffic congestion. MTR was authorized to proceed with the project in 2010 and the construction of the new rail line commenced in 2011.



The Contract

The alignment of KTE will be extended from the existing Yau Ma Tei Station to Whampoa via Ho Man Tin with 2 new stations to be built. The contract of construction of Ho Man Tin Station and tunnel from Yau Ma Tei to Whampoa, which is numbered 1001, was awarded to Nishimatsu Construction Company Limited, while Chun Wo – Hip Hing Joint Venture is in charge of the contract of construction of Whampoa Station and overrun tunnel, the numbered 1002. The project is underway at a cost of around HK$5.3 billion (in December 2009 prices).



Construction
of the Tunnels

The 2.6 km long KTE will operate entirely in subterranean tunnel. Beginning from Yau Ma Tei Station, the alignment will run through Gascoigne Road and Wylie Road and link up Ho Man Tin Station at the site of the ex-Valley Road Estate. It will then run along Chatham Road North, Wuhu Street and Tak Man Street and reach the terminal station at Whampoa. The construction of the twin-track tunnel with a diameter of 10.8 m span from Yau Ma Tei to Ho Man Tin will be started from the temporary work site at Wylie Road. As for the 9.8 m span platform tunnel and 5.8 m to 7.1 m span overrun tunnel from Ho Man Tin to Whampoa, the excavation will commence from Fat Kwong Street Playground temporary work site.



Station Design

Located approximately 24 m underground with 8 levels, Ho Man Tin Station will be an interchange station for the Kwun Tong Line Extension and the future Shatin to Central Link. The station adopts cruciform design for smooth passenger flow. Kwun Tong Line will be arranged at the lowest level, while the upper level will serve Shatin to Central Link. An interchange concourse will be set up in between the two platforms and different levels are connected by escalators. The station is served by a total of 5 entrances, which are located at Chung Hau Street, Chung Yee Street, Yan Fung Street, Chatham Road North and Fat Kwong Street. The entrances and station concourse are above ground.

Whampoa Station, which connects the road surface to the underground platform situated as deep as 20 m down the earth with 2 levels, will be the terminal station for the future Kwun Tong Line. In order to avoid serious traffic impact caused by extensive road excavation, split concourse design will be adopted. The concourse of Whampoa Station will be divided into East and West Concourses, which are located at the junction of Shung King Street/Tak On Street and Hung Hom Road/Tak Man Street respectively. The lower level is single-sided platform to tackle geographical constraints.



Pedestrian
Link Facilities

To improve the connectivity between Ho Man Tin Station and areas in the vicinity, several pedestrian links will be established. A pedestrian subway along Fat Kwong Street and a covered footbridge across Chung Yee Street will be built to connect a footbridge to Ho Man Tin Estate and Oi Man Estate respectively. A covered footbridge crossing Chatham Road North will also be constructed to link up Ho Man Tin Station and Wuhu Street. Residents from Wuhu Street can even go to the residential area at Ho Man Tin via the walkway at the non-paid area in the station. Barrier-free access and escalators will be provided for people in need.



Construction Methods

Different construction methods, including drill and blast, mechanical excavation, cut-and-cover and open blast method are adopted in the tunnels construction works. A 120 m long single-track tunnel and a 1,765 m long twin-track tunnel from the new rail line will be built by drill and blast method. This method is suitable for excavating hard rocks, as well as requiring less working area and construction period. To deal with the narrow construction environment, jumbo drilling machine which is 10 tons in weight and 6 m in length is introduced to expand the existing cable tunnel at Yau Ma Tei Station.

Tunnel constructed by mechanical excavation is roughly 320 m in length, which covers part of the platform tunnel at Whampoa Station and the overrun tunnel. Mechanical excavation brings less vibration, noise and pollution, therefore carries less impact to road users and avoids damage to the existing buildings.

For Whampoa Station, the concourses and platforms will be constructed by cut-and-cover method, which accounts for approximately 240 m in length. Steel pipe piles will be installed in advance before bulk excavation. While the excavation is implemented underground, temporary road decks will be placed on the original road surface to maintain smooth traffic flow.

Open blast method will be applied to the construction of Ho Man Tin Station. After excavating the upper soft ground near the surface, station will then be built by open blast method in deeper rock layer. With a shorter construction period than mechanical excavation, it can effectively speed up the progress and therefore reduce disturbance on construction nuisance. Protective measures such as temporary vertical screens and blasting cages will be installed and the impact from blasting operations on nearby buildings will be strictly monitored.



Challenges

Since the construction works will be carried out in the districts that are highly populated and frequently congested, MTR has to keep to minimum the impact on road users and nearby residents. An independent consultant has been appointed to conduct environmental impact assessment study and provide suggestions on mitigation measures to reduce the negative influences which might cause by the project, such as watering and covering stockpile areas to suppress dust, adopting quiet plant and erecting noise barrier to lessen noise level, etc.

On the other hand, MTR will regularly report the information of the Temporary Traffic Management Scheme at the District Council and the Community Liaison Groups meetings. Notice will be given out beforehand to inform the commuters for each temporary traffic arrangement. “MTR Kwun Tong Line Extension Newsletter” is also issued to enable the public to better understand the details and progress of the project.



Environmental Protection

Several eco-friendly designs will be adopted to coordinate with sustainable development. For example, the valley-shape alignment track design reduces energy consumption for train operations by 2 to 3% since it allows trains to accelerate and decelerate naturally when travelling downhill and upslope. The energy from downward lifts and escalators can be regenerated into electricity for other station electrical and mechanical utilities by using power regenerative system and this helps diminish 10 to 20% energy consumption. Water-cooled air-conditioning system and LED lighting system will also be introduced to use 10 to 20% and 20 to 30% less energy respectively.

On the other hand, greening works will be launched within the site area of the project. An approximate total of 55 m2 of vertical greening will be offered at Ho Man Tin Station. Meanwhile, around 2,900 seedling trees and 11,300 shrubs will be planted on slopes near Ho Man Tin Station.

Progress and Conclusion

The construction works for KTE are progressing steadily and the new rail line is scheduled for commissioning in 2015. Upon completion, it is expected that the KTE will generate HK$400 million economic benefits annually.



Courtesy acknowledgement:
MTR Corporation Limited
for providing the above information and photos