Final Report - Asian Development Bank

Ho Chi Minh City Metro Rail System Project Final Report - Revised
Management Authority for Urban Railways Chapter 4 – Proposed Metro Line
94. The line remains underground on Truong Chinh past the end of the Tan Son Nhat airport
runways, and then surfaces through an open cut transition area of around 230m just beyond Truong
Chinh 1 station. The line runs on viaduct along the centre of Truong Chinh until it terminates just
beyond the spur connection to the Tham Luong depot.
95. As currently planned, the northern end of the viaduct is offset from the road centre-line due to
the limited curvature possible on the crossover at this location, and this results in the need for portal
column supports across the road. Another option would be to extend the line around 200m further
north until the crossover can be located on a straighter section of road; this may make good sense if
the Line is to be extended northwards in future, and it is suggested that this issue is reviewed at the
next design stage.
4.4.3 Alignment Design Issues
96. General constraints on the alignment include:
As the typical stations have an island platform due to the choice of twin tunnels, the width
of platform fixes the spacing of the twin tunnels centre lines: 16.5m. Nevertheless, as it is
explained hereunder, spacing has to be reduced to 10.5m in order to limit the influence of
tunnels on existing fiction piles supporting buildings of second row. Therefore the
alignment out of each station has a curve and counter-curve to reach the 10.5m spacing.
For passenger comfort, it is avoided as often as possible to overlap horizontal and vertical
transition curves. As it has been considered more important to have first the tunnel dive,
the alignment with a 16.5m spacing is kept from the station platform end till the end of the
vertical transition curve.
97. Particular constraints on the alignment are as follows:
a radius of 250 m has been set between Ben Thanh and Tao Dan to avoid a friction pile
on the north side of the street and to avoid going under the New World hotel.
a radius of 250 m has been set before Tao Dan station on Ben Thanh direction to avoid
running the tunnel under buildings
A crossover for temporarily reversing trains in case of problems on one portion of the line,
is implemented, east of Hoang Van Thu. This crossover starts within the station Hoang
Van Thu in the technical rooms area. This crossover is a constraint for the alignments
since it requires more than 200 m of straight line.
A garage with a crossover is implemented, east of Ben Thanh. It encompasses two side
tracks for future extension of the line towards Saïgon river, a garage track “Y” shaped for a
6-car train, 2 switches and a double switch. Its overall length is 225 m
A transition zone, West of Truong Chinh, makes horizontally the two single track merge
into a double track tunnel box and vertically raise the track level to reach ground level.
A switch on each track is implemented West of Tham Luong station to join the main line,
on viaduct, to the double track, on viaduct, connecting the depot
A crossover is set, west of the junction between the main line and the connection to the
depot for reversing trains. In order to shorten the length of viaduct which not commercially
operated, the crossover is implemented as close as possible to the connection to depot.
As the crossover needs to be set on a strait line and as a straight line has to be set
between two turn out, the viaduct alignment can not be in the axis of the avenue. As a
matter of fact, the bearing of the straight line is fixed by the Tham Luong bridge.
A radius of 160 m is set for the tracks of the viaduct connecting depot. The track has no
cant since trains are operated without passengers at a reduced speed. 160 m is also the
radius of the switches of the turnouts.
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