By Vincent Tse, Hong Kong, 852-2856-8899, tse.vincent@pbworld.com; Kenneth Li, li.kenneth@pbworld.com; and Vincent Han

The Kim Chuan Facilities Building located at Kim Chuan in Singapore serves three rail lines that are planned to operate as fully automated train services with no drivers on board the trains—the Marina Line (MRL), Circle Line (CCL) and future Eastern Region Line (ERL). The building has a floor area of more than 100 000 m2 (1 million square feet), much of which is built underground. It is more than 1 km (3,200 feet) long, approximately 150 m (500 feet) wide at midpoint, and more than 20 m (75 feet) below ground at track level in some locations. Its functions include administrative offices, including staff training school and amenity facilities (changing rooms, canteen); control centers; and underground maintenance and stabling facilities. The building site is bounded by roads either existing or planned on all four sides in addition to a large building and drainage culverts to the west.

The focus of this article is on the maintenance facility, where trains will be cleaned, serviced and overhauled, and on the stabling facilities, which were planned to for a minimum of 70 trains. Many concerns were raised about features of the original design, particularly smoke extraction, evacuation of employees and access for fire fighters in the event of an emergency. PB was commissioned as an MEP consultant and fire consultant to improve the building design and address these concerns.

Original Scheme

The preliminary design was based on a two-level stabling yard that has berths for approximately 70 trains and can be accessed from the west via the upper and lower approach tracks and from the east via the eastern head shunts (Figure 1). Works locomotive sidings and major workshop facilities were located at track level with minor workshops and administration office at the upper level. Mechanical and electrical (M&E) plant rooms were located at an intermediate level underneath the ground level. The upper facilities building level was located below the existing ground level with a series of sunken courtyards providing natural light to the underground facilities. Storage facilities were accessed by an automated storage and retrieval system spanning all levels, and general storage areas for heavy or large items were provided at the track level workshops.

Smoke Extraction. A dynamic smoke extraction system was designed in the original scheme to cater for the train stabling areas, maintenance workshops and material storage areas. A whole floor of mechanical plant room was reserved, as shown on Figure 1. Due to the relatively low headroom design of 6 m (20 feet) high for the two levels of stabling floors, smoke extraction systems were composed of the extraction fans and the fresh air make up fans. All were interlocked in each respective smoke zone to serve for smoke management functions. In the stabling areas, there were 20 smoke zones to confine the smoke zone area within 2,600 m2 (28,000 square feet) according to the regulation requirements. Extraction ductwork had to be located at a high level while fresh air supply outlets were designed at a low level for fresh air replenishment.

Figure 1: Original Scheme of facilities buildings layout (top) and section (bottom).

Evacuation of Employees. As most of the areas were to be built underground, the means of escape relied on the staircases, which had to be designed to reach every level of the facility. Evacuees in the upper stabling tracks had to make use of the staircases that led to the mechanical floor, which was also used as temporary transit to the ground level. In the lower stabling tracks floor, evacuees had to escape via the passageways that ran under the stabling tracks and then connected up to stairways at the end of the basement before they were discharged to the outside. In general, due to the construction of the various levels of basement for the stabling floors, the means of escape were indirect, and staff would have to be carefully trained to fully understand the layout and know where to go in case of emergency.

Access for Firefighters. Similarly, as the access route for firefighters made use of these safety staircases, their means of access was also very complicated and made it difficult for them to correctly locate the fire site. As a result, the time required for the fire fighters to attend to the fire site was long.

New Scheme

PB revisited the whole scheme with the intent of improving the building design and developing a system that was more cost-effective, provided for more simple system operations, and was more environmentally green in nature. Using concepts of fire engineering and green engineering, many changes to the schemes were brought to the building design.

Air Gaps. As the facilities building is a long form, two long continuous air wells 2 m (6.5 feet) in width were provided, one at each end of the building. These air gaps provided:

• Fresh air inlets for the basement such that air could be drawn in naturally. That meant only extraction fans were required for the mechanical ventilation system serving for the basement—all fresh air intake fans and the related ductwork system could be deleted.
• Fresh air replenishment for the smoke extraction system in the event of fire. That meant only smoke extraction fans were required for the smoke control system.
• Natural lighting to the workshop areas and train stabling levels. This light improved the visibility of the basement environment. In the event of fire, evacuees running under the air well will be less panicked than they would be in the other basement area. The vehicular access road designed under this air well in the basement level can be considered as safe passage through which evacuees can make use for escape.

Performance Approach. The smoke extraction systems serving for the stabling areas and the workshop were designed in accordance with a performance approach¹ in consideration of the following factors:

• The design fire size was assumed to be under the control of a sprin kler-controlled fire scenario. By using a fast response sprinkler head, the fire sizes adopted in various areas were lower than the original scheme design assumptions. Thus, the smoke extraction rate could be reduced.
• Smoke zone areas were increased with the justification by computational fluid dynamic simulation when we took account of the high ceiling headroom of the area concerned. This change reduced the number of smoke extraction systems required due to the reduction in smoke zones.

Simplified Design. Taking account of the elimination of fresh air intake system, decrease in design fire size and the reduction in smoke zones required, we were able to design the smoke control system and mechanical ventilation system following a much more simple approach. All of the mechanical fan rooms previously reserved could be deleted. Instead, only small fan rooms were designed at a high level in the serving areas.

Easier Construction. By consolidating the reduction in mechanical floors and the reshuffling of the plant locations of the facilities building, we worked out a scheme with only one stabling track floor. This further improved the design in particular regarding construction constraints such that, basically, only one basement level was needed when compared with the previous scheme of three basement levels.

Conclusion

The following advantages were brought along to the project due to the design improvements:

• Simplicity in design and operation of the smoke extraction system and mechanical ventilation system
• Easier construction with only one basement level of stabling tracks
• Improved indoor environment with more natural light and naturally drawn fresh air from ground level.

• More direct and straight-forward means of escape for evacuees and access for fire fighters in case of emergency. Fire fighters can easily locate the fire site and reach it in the shortest time. In the worst situation, means can be provided to allow the fire engines to reach the basement via the vehicular access road.