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Category 2: Civil Structures
Background
The project Doorstroom (Thoroughfare) Station
Utrecht (DSSU) includes optimising the current railway
infrastructure on the site of Utrecht Central Station.
Part of this plan is a service tunnel, which connects
the public road with the southern rail yard. This
underpass crosses four tracks and is built with minimum
disturbance to normal train traffic.
On behalf of ProRail, the DSSU project is designed
by Movares and will be executed by the contractors
combination U-Central (BAM Rail and Volker Rail). The
design phase includes the preliminary design, the final
design and the implementation design.
Implementation
The service tunnel is made up of 8 segments. The
tunnel ramps consist of 6 open tunnel segments parallel
to the tracks. The junction with the train tracks consists
of 2 partially closed segments. The partially closed
segments include a section in which the road turns the
corner at 90 degrees. Under segment 4 there is a pump
basin for rainwater.
Due to the high water table a sheet pile pit is needed
since lowering of the groundwater level is not permitted.
After unearthing of the pit and the pouring of the
underwater concrete the pit is drained. For driving the
sheet pile along the tracks there is 1 train-free period
of 52 hours available. To build segment 5 in its final
location there will be approximately 7 months when
2 of the 4 tracks will be out of service. This segment
can be built relatively simply without disturbing the rail
traffic. On the other hand, segment 4 must be built
during a train-free period. To that end, the deck west of
the railway tracks will be built on top of the sheet piles
and during a 52-hour train-free-period slid on to its final
place. The deck is located temporarily on the sheet
pile walls, which are part of the building pit. Afterwards,
the pit under the deck is unearthed. Then underwater
concrete is poured and drained after the concrete
has been sufficiently cured and the finishing work can
begin. This phase consists of building the pump basin,
building the concrete walls and floor underneath the
deck, when once again a train-free period in needed.
Finally, the sheet piling is disconnected from the newly
built segment to ensure that all external forces will be
distributed to the new segment.
Design
During the entire design phase engineering programs
such as Allplan (drafting) and Scia (design) were used.
The final design consists of a model where fabrication
and reinforcement drawings can be generated. It is
intended that this data can be transferred completely
to the contractors combination U-Central so that
information loss in the digital chain is reduced to a
minimum.
The tunnel floor has both a longitudinal and transverse
slope and goes through a bend in the tunnel. The floor
reinforcement is orthogonal and follows the upper
surface of the floor.
The project is designed in accordance with the latest
European standards (EC2) and, where possible, the use
of standard lengths of rebar.
Service Tunnel Station - Utrecht, The Netherlands
Software: Allplan Engineering, Scia Engineer
