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The segment precast plants
The installation of segments (point) while the TBM progresses, requires a constant supply of segments
Any stopping of the TBM due to lack of segments or poor segment quality would be disastrous
and very expensive.
On the other hand, time is a key factor for concrete maturity. Even with the curing room methods required due to time limit reasons,
the segments need to be stored for nearly a month before they can be used for the tunnel, and this
in order to ensure the concrete maturity that will allow its mechanical resistance.
Segment engineering is a process that represents an important part of the tunnel project, it requires the setting up of a precast plant, either a stationary or a carrousel-automated one.
The choice between those two techniques is often cost or time driven.
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Whatever the choice made by the contractor with the CBE engineering department, the segment precast plants
require high handling capabilities, due to size and weight of the materials to be handled.
Furthermore, the segment is casted with the extrados in down position and it must be turned for its future use by the TBM which requires important handling with sophisticated reverse equipment.
During a tunnel project, the infrastructure needed by the segment manufacturing plant is huge,
and its impact on the whole planning is quite significant.
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Stationary precast plants
With this option, moulds stay at the same spot during the whole building process.
Which means to bring for each mould and for each concreting operation:
» the required tools (pins, sockets, etc...)
» the reinforcement
» the needed concrete
It also implies constant movement on the worker's part to reach the designated mould.
For each type of tunnel, specific segments and specific moulds.
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The same concerns the demoulding process where heavy handling is required to bring the segment to its finishing station
(reversal, glueing gasket) and storage yard.
This option, called " stationary workstation " is therefore chosen for short term projects
(several months) or in low labour-cost countries
Stationary workstation reinforcement assembly
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Carrousel precast plants
With this option, moulds are automatically conveyed towards the designated workstation:
» Preparation (lubrication, accessories)
» Laying out of the reinforcement
» Concreting cabin
» Polishing
To be then transported to the curing room where they remain for 5 to 10 hours, depending on the concrete
attributes and the segments size (thickness), before returning to the production line where the segment will
be removed from the mould on the designated workstation.
This system enables a 30 to 40% increase in productivity, especially relevant for high labour-cost countries.
It also ensures a higher production rate for the same number of moulds. One can in fact " deliver " a segment
each 8 or 12 minutes, which is almost impossible with the " stationary workstation " scenario.
Another advantage of this technique that can be underlined, is the noise reduction of the concreting vibration, as
the concreting is done in a sealed space (the concreting cabin).
All the handling is driven by a highly capable and reliable robot.
The robot is linked by modem to our automatism-work shop, which enables remote adjusting and corrections in case
of potential electronic/automatic anomalies.
Carrousel for reinforcement
The production of reinforcement cages is a cumbersome task that requires a lot of manpower or costly equipment,
which is sometimes irrelevant for a particular project.
CBE offers semi-automatic medium alternatives to the reinforcement production.
A reinforcement distribution system (manège) is usually installed on the automated segment production lines (carrousel) in order
to ease the reinforcement transportation and its installation in the moulds.
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Carrousel precast plants
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