West Rail – Part 7 Construction North
Tymon Mellor: Following a ground breaking ceremony held in October, 1998 construction of West Rail gathered pace. The southern section of the line was in tunnel, while from the northern tunnel portal in Kam Tin, the route passed through the at grade depot before adopting an elevated arrangement, approximately 13.4 km, between Kam Tin and Tuen Mun. Construction of the northern section of West Rail had many technical challenges to meet the programme, along with the risk of flooding, and also the presence of marble cavities impacting foundations.
CC-601 Depot Civil and Infrastructure Works
The Depot occupies an area of about 32.5 hectares of land and provides an integrated maintenance facility for rolling stock, infrastructure, and railway buildings. The facility includes stabling and first, second and third-line maintenance of all types of rolling stock, including provisions to expand in the event of the Phase II project works. The complex comprises:
- EMU Maintenance Building;
- Locomotive Maintenance Building;
- Infrastructure and Building Maintenance Building;
- Permanent Way depot;
- 18 EMU stabling sidings;
- 2 train washing plants; and
- underfloor wheel truing machine.
The land for the depot was predominately private land with minor areas of government ownership, and was prone to flooding. Land acquisition was a sensitive issue and on the day of handover, some 200 police officers were deployed but the process proceeded without incident. The land was handed over to the contractor who proceeded to demolish the buildings and clear the vegetation and trees. The first major works was the construction of a new major drainage nullah around the maintenance buildings and a 300m long multi-cell box culvert passing below the tracks, and a total of 4.1km of drainage channel was required.
On the 14th April 2000, 430mm of rain fell in the northwest New Territories, severely impacting the depot earthworks and causing flash flooding within the wider communities. The Drainage Services Department (DSD) noted that flooding was in close proximity to West Rail works[1], and this was sufficient for the project to be blamed for the flash flooding of private property. To avoid future blame as well as to better protect the works, a new set of drainage impact protocols were implemented by the West Rail team. Arising from was the drainage task force jointly established by DSD and KCRC to assist and monitor all project contractors in respect of flood prevention measures, as described in the previous article.
West Rail Depot (2001)
Several small roads within the site had previously been consolidated into the new Pat Heung Road, as part of the earlier Route 3 construction works. The new road serves the new Tai Lam Tunnel toll plaza and had to be always maintained, and this requiring the construction of a 660m long road viaduct, 18m above the West Rail tracks to provide the necessary grade separation. In addition, new perimeter roads were required around the site along with internal access roads within the depot, necessitating a total of 14km of new road construction.
With the completion of the site formation works, access was provided for the construction of the depot buildings by CC-604 and the track work contract CC-1820. Work continued with the construction of the noise barrier and drainage works around the site.
CC-604 West Rail Depot
The key building of the depot was the EMU building, at over 700m long with a gross floor area of 41,000m2 this was where the trains would be maintained. However, it had a more immediate use, as it would be used to check and commission the new rolling stock as and when they were delivered from the overseas supplier to Hong Kong. The building was completed in early 2002 ahead of the arrival of the rolling stock in April 2002.
Pat Heung Maintenance Centre (2002)
The term depot was considered unsuitable by KCRC management, preferring the term Maintenance Centre, and thus all depot facilities were renamed and the West Rail Depot became the Pat Heung Maintenance Centre.
CC-602 Kam Sheung Road Station
Located in a rural area scheduled for future development, Kam Sheung Road Station was proposed as a future interchange for the regional train to Shenzhen, the northern shuttle extension which would link to East Rail along with the passage of freight traffic. The station and associated facilities were designed to accommodate a large future property development around the station. The structure was entirely above ground, two stories high with a plan to integrate with the future residential development, the station will become hidden under a large landscaped deck.
Kam Sheung Road Station (2000)
The island platform station had provision for a third platform and elevated approach alignments from the north for the interchange and through running required for the West Rail Phase 2 services. The Phase 2 works have now become the Northern Link, and is currently being developed by the MTR. However, the new line is now proposed as an underground alignment rather than the elevated arrangement assumed for the West Rail Phase 1 enabling works.
Kam Sheung Road Station
For many, the station is considered to be the simplest and most functional on the line, with the terracotta tiling matching with the rural setting of the structure. The station adopts a ground level concourse with platforms and tracks at first floor level and plant rooms on the roof level. The cast in situ reinforced concrete frame and slab superstructure is supported on bored piles. Parking facilities and a public transport interchange to serve the station was included.
Kam Sheung Road Station Platform Level (2023)
CC-603 West Rail Headquarters
The new railway required a headquarters to house the operations team and the support groups necessary to run a modern railway. The building would also house the operation control centre (OCC) and associated equipment room, the heart of an automated railway. The facility also hosts the incident management room where the different authorities required in the event of an incident would gather and coordinate their responses.
The OCC would operate 24/7 with seven staff on duty during operational hours managing the signalling, communications, control equipment, train operations and traction power supply. A large 8.2m by 2m mimic wall display provides a view of train operations along with real time information and CCTV. Programmable work stations provide details on individual systems and allows the operator to monitor and in some case remotely manage thousands of items of plant and equipment.
Operational Control Centre (2003)
The eight-storey building has a floor area of 12,770m2 with capacity for 400 staff and includes a canteen for operating staff, a lecture theatre, training facilities, a library and an exhibition hall. Given the presence of the OCC, the building needed to be secure, robust and resilient. The structure was designed to a high level of fire resilience and the use of gas cookers in the canteen was banned to avoid a possible gas explosion.
Work on the structure commenced in March 2000 and the building was topped out in late June 2001, allowing the Occupation Permit (OP) to be issued in September 2002. With the OP in place, access for the railway systems contractor was provided for them to install their equipment and commission the control room ready for the first staff to move in just before Christmas 2002.
Image of West Rail HQ (2003)
Viaduct Sections
The main 10 km of viaduct works were contained within two construction contracts, CC-201, which runs between Kam Sheung Road and Tin Shui Wai stations, and CC-211, which runs between Tin Shui Wai and Siu Hong stations. In addition, a short 600 m length of viaduct of the same design was contained within contract CC-213, between Siu Hong and Tuen Mun stations.
The KCRC’s appointed detailed design consultants prepared a design solution addressing the onerous constraints imposed by the environmental noise mitigation requirements and requiring a construction methodology common amongst Hong Kong contractors.
Viaduct Erection near Tin Shui Wai (2001)
As part of their bidding strategy, the joint venture of Maeda–Chun Wo employed Robert Benaim and Associates (Benaim) to develop a more economic design solution as an alternative design of the viaduct[2]. For the alternative to be considered, it was essential that an authoritative report that analysed the noise and vibration performance of the proposed alternative would match or better the performance of the conforming design. The alternative also had to address the normal design criteria including resisting overturning in typhoon winds of up to 79 m/s with the deck surmounted by a full noise enclosure, 11·5 m in the air.
Comparison of Conforming and Alternative Deck Sections
Following a number of analytical studies, it was concluded that the cross section of the viaduct could be revised, making a substantial saving in materials. To save on support bearings, it was decided to make the pier heads monolithic with the bridge deck for the standard spans, thus saving on bearings but also reducing maintenance costs. This approach required each span to have a dedicated column forming a portal frame, on a common foundation.
Typical Elevation for the Alternative Viaduct Design
With the endorsement of the alternative design, the contractor proceeded with construction achieving the predicted production rates of deck spans in as little as two days per span. With the success of the alternative design on contracts CC-201 and CC-211, the same design was adopted by the contractor for CC-213 for the construction of the 600 m length of viaduct between Siu Hong and Tuen Mun stations.
The outside of the viaduct parapet was designed with horizontal groves running along the length of the structure. The architects insisted that this detail would visually reduce the bulk of the structure, but there was concern that water would collect in the groves, resulting in staining of the concrete. The risk was minimised with the application of a suitable coating but for the Ma On Shan Line, the groves were vertical to avoid the risk.
Viaduct Parapet Detail
Two forms of viaduct erection were adopted, an underslung gantry suspended between two piers allowing pre-cast concrete segments to be placed in position and stressed together. The segments were either lifted directly into place with an adjacent crane or delivered using a lifting gantry running on the frame.
Underslung Viaduct Erection Gantry (2001)
Where longer viaduct spans were required, such as across a nullar or road, a balanced cantilever approach was adopted. From a central pier the precast segments were incrementally added in alternative direction to balance out the loads.
Viaduct Erection Using Balanced Cantilever Approach (2001)
The first span of the viaduct was erected in May 2000 and all spans, 13.4km were completed by December, 2001[3]. With a maximum height of 26m, the viaduct required 748 piles, one of which was 80m deep. The viaducts were assembled using the glued segmental segments that were precast in Dongguan, China. The production line for the viaduct segments was 700m long, and required 600 workers to cast the 8,728 units.
CC-202 Yuen Long and Long Ping Stations
Yuen Long Station is located at the eastern edge of Yuen Long town, with Long Ping Station close by to the north of the town centre. These stations are elevated with associated public transportation interchanges situated at ground level. The concourses are located at first floor and the platforms at second floor level with the tracks entering the stations along viaducts adjoining both ends of the stations.
The station at Yuen Long was designed to support a property development directly above the station. In an geological area notorious for underground marble cavities, this required the use of very deep large diameter piles to provide support for 25 and 38-storey tower blocks which will eventually stand on the roof of the station. End bearing foundations with at least 20m of solid rock below the toe are not too difficult to achieve in typical Hong Kong granite, but Yuen Long where a pile is bored in marble and passes through a cavity, it was necessary for the piles to go deeper until 20 m of solid rock was identified. The ground conditions turned out to match the worst-case scenario and it was necessary to install deep piles across the whole site, a total of 123 piles of 2.5-3 m diameter were taken to a depth of up to 120 m. Possibly the worst locations in Hong Kong to build a high rise residential development!
Yuen Long Station
At Long Ping Station, the principal challenge was presented by three nullahs, a large one that crosses the site and two that run parallel to the railway line. The Drainage Services Department required box culvert construction and foundation works in the nullah to be confined to the dry season, due to the risk of flooding during the wet season. As a result, the contractor only had six months out of each full calendar year to complete the installation of deep piles and the construction of culverts.
The station superstructure comprises cast in situ reinforced concrete frame and slab structures with deep longitudinal beams. The roof structures consist of curved steel ribs supporting metal cladding. As with Yuen Long station, marble cavities were a risk, with one record breaking pile being over 140m long.
Long Ping Station
The need for long piles at both stations resulted in delays to the programme. To catch up, the contractor for the two stations deployed more than 1,000 workers on the two sites at the peak of construction. Superstructure construction was relatively straightforward by comparison; Long Ping’s distinctive curvilinear portal frames for example were erected quickly in sections. The two stations were topped out in July 2002.
CC-203 Tin Shui Wai Station
Tin Shui Wai Station was built above an existing road junction and Light Rail tracks, with a school within close proximity. In common with other stations, the platform edges are enclosed by platform screen doors, which open and close together with the train doors, enabling trains to stand alongside the platform in an openair environment, and thereby reducing the width of the station footprint.
Tin Shui Wai Station in the background
CC-212 Siu Hong Station
Siu Hong Station is located at the northern fringe of Tuen Mun New Town, adjacent to the existing Siu Hong Light Rail stop, and is a major interchange station with the Light Rail network. Located within the Tuen Mun Nullah, the foundations consist of bored piles extending above the nullah invert up to adjacent ground level to support the platform slab. The piles were constructed within a temporary cofferdam in the nullah, and since the temporary works would reduce the nullah’s hydraulic capacity, the foundation works were only permitted to be carried out during the dry winter months with cofferdam sheet piling and access ramps removed before the onset of the wet season. Foundation works progress were therefore critical to the overall construction programme. The station superstructure was a cast in situ reinforced concrete frame and slab structure. The roof for Siu Hong Station is a double pitched steel frame structure clad with profiled metal sheeting.
Siu Hong Station
Siu Hong Station includes a major interchange facility with Light Rail, which was designed as a triangular shaped steel structure projecting from the West Rail station. Because the interchange was located close to a residential development and was being built over operational Light Rail tracks, work could only be carried out during LRT non-traffic hours without disturbing the residents.
Siu Hong Frame Above the LRT Tracks
The structure involved the erection of 1,000 tonnes of steel above the tracks, but there was concern from both EPD and the District Council that the installation works would be too noisy at night.
To minimise disturbance, the structure was broken down into smaller components which could be bolted together almost like a giant Meccano set. However, even this approach was rejected by EPD as the noise generated during normal steel erection was a serious concern, particularly with the close proximity of the Siu Hong Court residents. After much discussion with EPD and the District Council an innovative arrangement was proposed by KCRC; to avoid the ‘pinging’ sound when hitting the fixing bolts into place and the ‘crash’ noise when lowering the steel elements into place the workers would adopt rubber mallets and rubber pads. The contractor was not convinced so a trial was arranged for the District Councillors to witness the results. Despite scepticism from the workers who were not used to changing their ways, the results were positive with a dramatic reduction in the amount of noise generated and councillors agreed to the approach.
On the first night of steel installation using this approach, EPD received a complaint about the construction noise. A quick review confirmed work had not yet commenced on the KCRC site and the noise was attributed to a new commercial development who were working late. Work commenced without incident and 130 nights of steel erection works were carried out effectively in the quiet environment without attracting any complaints of noise nuisance. As Ian Thoms said, “We rented a flat there and set up a continuous noise monitoring system to get an accurate picture of the noise impact on residents. We worked very closely with the District Council and the community throughout the project. The project was a testament to the excellent relationship we had with the contractors and the residents”[4].
Completed LRT Structure
CC-213 Tuen Mun Station
The station sat over the nullah passing through Tuen Mun, a 550 m long elevated structure, included the over-run and ramp structures. As part of the contract the existing Light Rail San Fat Stop was rebuilt on elevated structure above Pui To Road to create a direct link with the Tuen Mun Station concourse. The old San Fat Estate was demolished by the contractor to be replaced by new commercial and residential development adjacent to the station. It was hoped this would trigger regeneration of the heart of Tuen Mun New Town. A number of other community facilities were constructed included a new school at Hoh Fuk Tong and San Wo Lane playground.
Tuen Mun Nullah Occupation (Nov’1999)
Same as for Siu Hong Station, construction of the station required the installation of piles within the 70m wide nullah. Following discussions with DSD it was agreed that the contractor could occupy much of the nullah during the dry season. A temporary barrier was built across the channel with the flow directed down the west side. The contractor mobilised a number of small piling sub-contractors using dated equipment. One contractor, with Singapore experience tried to use an auger to excavate the pile. This did not work in the complex Hong Kong ground conditions. By the end of the first dry season the contractor was behind schedule and requested an extension from DSD of the nullah occupation.
Tuen Mun Piling Within the Nullah
DSD granted a few more weeks, but on the 14th April, 2000, just two weeks into the wet season there was intense rain fall in the north-west New Territories, resulting in heavy water flows which flooded the temporary construction site and submerging a number of the piling rigs. By the start of the following dry season, the contractor had contracted Gammon Foundations to complete the work. Gammon mobilised sufficient equipment to make up the lost time and completed the piling works on programme.
Tuen Mun Completing the Station Deck Above the Nullah
The original station design included three tracks to provide capacity and flexibility for the line, but one of the value engineering initiatives adopted was to drop the third track, and to provide sufficient enabling works for it to be built at a later date, if required. The length of the nullah portals and junction to the viaduct structure were adjusted to reflect the future requirement.
Tuen Mun Station
While the civil works were under construction, the railway systems contractors were completing their designs, procuring and manufacturing equipment, ready to start on site. As the civil works reached completion, the systems contractors were provided with access, and now the teams would discover if all the planning and coordination would be a success or like some other projects, would just expose errors, delays and additional costs.
Sources
Flood Chaos Linked to West Rail, SCMP, 19 May 2000 ↑
- Development of an alternative design for the West Rail viaducts, J. H. Cooper and M. F. Harrison, ICE, May 2002
- KCRC West Rail, Hong Kong, UCL Project Profile, University of Hong Kong.
- Against the odds: West Rail topped uot all stations, http://www.hkengineer.org.hk/issue/vol30-nov2002/cover_story/
This article was first posted on 12th October 2023.
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