Preliminary design has been completed for an underground road system for the central area of Singapore (Fig 1). Construction is anticipated, possibly in stages, early in the next century.
The underground road system will include 40km of tunnels to form a 15km ring road under the city of Singapore, carrying two lanes of highway traffic in each direction. A series of 33 entry/exit ramps connect the tunnels with the surface streets. The planning and design of the system was based on achieving three principal goals:
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- To increase highway capacity by 40% plus to accommodate projected traffic for 2030.
- To allow through traffic to travel uninterrupted around the city and by-pass some of the busy streets and intersections
- To have negligible environmental impact
The underground ring road solution was selected after review of 11 alternative transportation networks and was identified as the solution that best satisfied the above goals.
Significant features of the tunnel network are:
- 40km of tunnels (one, two and three lane)
- 31.5km cut+cover, 8.5km bored
- 5km of depressed road entry and exit ramps
- Three underpinned or supported structures
- Five crossings above or below existing MRT tunnels
- 12 ventilation buildings and nine ramp ventilation structures
- Three new and four reconstructed bridges
- 21 re-configured surface street intersections
- A single control centre for monitoring the system
The tunnels pass through extremely variable geological formations and a variety of cut+cover and mining methods will be used. Longitudinal ventilation is provided by 12 ventilation buildings and nine ramp ventilation structures.
Construction of the bored tunnels some 13-14m in diameter will mark another milestone in Singapore’s tunnelling technology.
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By GlobalDataDeep Tunnel Sewerage System (DTTS)
The overall concept is to construct cross-island deep tunnels to intercept the flows in existing gravity sewers, upstream of the pumping stations, and channel them by gravity to two new centralised sewage treatment works at the southeastern and southwestern coastal areas. All the treated effluent will be discharged through deep sea outfall pipelines into the Straits of Singapore.
When the DTSS is constructed, the sewer reticulation system in Singapore will consist of only gravity sewers linked to deep tunnels. All the existing sewage pumping stations will be phased out, as will the six existing treatment works.
The preliminary proposal of the deep tunnel system will comprise the following four components:
- Two cross-island large deep tunnel sewers, 5-6m i.d. (Fig 1).
- Two centralised sewage treatment works, which will eventually replace the existing treatment works
- Deep sea effluent pipelines into the Straits of Singapore
- Link sewer network
MRT Marina Line
A new underground railway line to serve the Marina Centre and Marina South areas is under design, and construction is anticipated to start in late 1999. Completion is scheduled for 2004 (Fig 1). The Marina areas are mainly reclaimed land adjacent to the CBD. Development of a new down town core area will be implemented early in the next century, and the Marina Line is required as part of the infrastructure to serve this important business hub.
The line will initially be some 15km in length, with 22 stations. Tunnel diameter will be approx. 5m i.d. Much of the construction will be in soft clays and reclaimed land, which may still be consolidating, possibly posing difficulties for construction. Architectural and engineering consultancy services were performed by a JV of Parsons Brinckerhoff and Mott MacDonald.
Civil contracts will be invited in the second quarter of 2000 at the earliest.
Underground Science City (USC) Centre
Detailed site investigation and design of an underground cavern complex under the Kent Ridge Park is currently being performed by the Nanyang Technological University and the Public Works Department. The cavern complex is to house science park buildings of five to six storeys comprising the Underground Science City (USC). The development of the USC will provide additional space needed for Research and Design orientated activities without disturbing the natural environment.
The subsurface conditions at Kent Ridge vary from sandstone, conglomerate and limestone, generally fractured, folded and faulted with weathering up to 70m deep. The Underground Space and Rock Mechanics research group at Nanyang Technological University has R&D programmes to tackle both design and technical problems involved in constructing large span caverns in a generally weak and fractured rock mass.
