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Floating Slab Track (FST) for Hamburg underground metro system
Extension of subway line U4 in Germany‘s second largest city Hamburg
When completed by the end of 2026, 13,000 Hamburg residents will be able to reach the city center by public transport with almost half the
travel time. In order for the line to be extended by two additional stops (Stoltenstraße and Horner Geest), the U4 must be branched off north. The extension of the line will take place in the immediate vicinity of the populated city center.
The underground network is operated by Hamburger Hochbahn AG, one of the biggest transport companies in Germany with over a 100 years of experience.
Challenge
Four switches and a crossing had to be retrofitted in an upstream existing tunnel for branching out line U4. The reconstruction phase was scheduled for 10 weeks and required the interruption of line U2 and U4.
Switches and crossings represent discontinuity points in the track, which cause additional strong vibrations in the trackbed. A residential area next to the tunnel had to be protected from resulting extra vibrations and structure-borne noise. The vibration expert in charge contacted us approximately 1.5 years prior to the execution to design and integrate a vibration isolating solution that could be installed within the reconstruction period.
Solution
GERB designed a state of the art vibration isolation solution by using floating slab track (FST) technology to protect residents from unwanted vibrations. Together with the executing construction company Otto Wulff Bauunternehmung GmbH, we installed a continuous FST slab with a length of 76 m (528 m²) in the tunnel. With 190 GSI spring elements the slab was lifted and decoupled from its surrounding structure to isolate vibrations resulting from train activity. The optimized GSI spring elements are suitable for particularly thin track slabs as the planning considered a slab thickness of only 28 cm.
Technical Facts:
Vibration source: Train Traffic in the underground system
Natural frequency: 9 Hz continuous slab (in-situ) in tunnel
Dead load: 4.9 t/m
Speed: 40 km/h
Implementation
The installation of a floating slab track can be easily integrated in the workstream of regular construction activities:
1.
A membrane must be laid over the entire surface of the area to be equipped with an FST. Alternatively a bond-breaker agent can be used instead. Next step will be positioning of GSI spring elements according to the design plans.
2.
Second step will be the placement of reinforcement bars before the pouring of the concrete. A final cleanup of the surface can now be performed with a dust blower to allow for optimal concreting.
3.
The pouring of conrete is the next step. The seperation between the concrete slab and the subgrade is achieved due to the placement of the membrane.
4.
As soon as the concrete has reached its required strength, the placement of GSI spring elements follows. Each housing is now equipped with its corresponding spring unit and shims.
5.
Final step will be the lifting of the slab. Our installation team supports you directly on site, with supervising or lifting. A special jack-up device is part of the GSI system and will be used to lift up every single slab. Completion of lift-up procedure results in floating slab track that allows the highest reduction of groundborne vibration and ground-borne noise to the surrounding structure.
- GERB vibration isolation solutions in trackbeds
Using a FST system with GSI elements is the effective way of controling ground-borne vibration and ground-borne noise directly a the source.
Our variety of trackbed isolation sytems will solve every possible vibration problem that you might encounter. We will be happy to provide you
with customized advice on your problem.
Result
After 10 weeks of construction, the U4 subway line as well as line U2 was put back into service on time. The success of the integrated floating slab track system could be determined by means of subsequent measurements. If you would like to have further information about the implementation or measurements, please contact us.
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Further Resources
You need further information on this topic?
Please do not hesitate to contact us with your individual question.
One of our project engineers will get back to you shortly.
Floating Slab Track (FST) for Hamburg underground metro system
Extension of subway line U4 in Germany‘s second largest city Hamburg
When completed by the end of 2026, 13,000 Hamburg residents will be able to reach the city center by public transport with almost half the travel time. In order for the line to be extended by two additional stops (Stoltenstraße and Horner Geest), the U4 must be branched off north. The extension of the line will take place in the immediate vicinity of the populated city center.
The underground network is operated by Hamburger Hochbahn AG, one of the biggest transport companies in Germany with over a 100 years of experience.
Floating Slab Track (FST) for Hamburg underground metro system
Extension of subway line U4 in Germany‘s second largest city Hamburg
The underground network is operated by Hamburger Hochbahn AG, one of the biggest transport companies in Germany with over a 100 years of experience.
Challenge
Switches and crossings represent discontinuity points in the track, which cause additional strong vibrations in the trackbed. A residential area next to the tunnel had to be protected from resulting extra vibrations and structure-borne noise. The vibration expert in charge contacted us approximately 1.5 years prior to the execution to design and integrate a vibration isolating solution that could be installed within the reconstruction period.
Challenge
Four switches and a crossing had to be retrofitted in an upstream existing tunnel for branching out line U4. The reconstruction phase was scheduled for 10 weeks and required the interruption of line U2 and U4.
Switches and crossings represent discontinuity points in the rack, which cause additional strong vibrations in the rackbed. A residential area next to the tunnel had to be protected from resulting extra vibrations and structure-borne noise. The vibration expert in charge contacted us approximately 1.5 years prior to the execution to design and integrate a vibration isolating solution that could be installed within the reconstruction period.
Solution
Technical Facts:
Vibration source: Train traffic in the underground system
Natural frequency: 9 Hz continuous slab (in-situ) in tunnel
Dead load: 4.9 t/m
Speed: 40 km/h
Implementation
The installation of a floating slab track can be easily integrated in the workstream of regular construction activities:
1.
A membrane must be laid over the entire surface of the area to be equipped with an FST. Alternatively a bond-breaker agent can be used instead. Next step will be positioning of GSI spring elements according to the design plans.
2.
Second step will be the placement of reinforcement bars before the pouring of the concrete. A final cleanup of the surface can now be performed with a dust blower to allow for optimal concreting.
3.
The pouring of conrete is the next step. The seperation between the concrete slab and the subgrade is achieved due to the placement of the membrane.
4.
As soon as the concrete has reached its required strength, the placement of GSI spring elements follows. Each housing is now equipped with its corresponding spring unit and shims.
5.
Final step will be the lifting of the slab. Our installation team supports you directly on site, with supervising or lifting. A special jack-up device is part of the GSI system and will be used to lift up every single slab. Completion of lift-up procedure results in floating slab track that allows the highest reduction of groundborne vibration and ground-borne noise to the surrounding structure.
- GERB vibration isolation solutions in trackbeds
Using a FST system with GSI elements is the effective way of controling ground-borne vibration and ground-borne noise directly a the source. Our variety of trackbed isolation sytems will solve every possible vibration problem that you might encounter. We will be happy to provide you with customized advice on your problem.
Result
After 10 weeks of construction, the U4 subway line as well as line U2 was put back into service on time. The success of the integrated floating slab track system could be determined by means of subsequent measurements. If you would like to have further information about the implementation or measurements, please contact us.
Solution
Technical Facts:
Vibration source: Train traffic in the underground system
Natural frequency: 9 Hz continuous slab (in-situ) in tunnel
Dead load: 4.9 t/m
Speed: 40 km/h
Implementation
The installation of a floating slab track can be easily integrated in the workstream of regular construction activities:
1.
A membrane must be laid over the entire surface of the area to be equipped with an FST. Alternatively a bond-breaker agent can be used instead. Next step will be positioning of GSI spring elements according to the design plans.
2.
Second step will be the placement of reinforcement bars before the pouring of the concrete. A final cleanup of the surface can now be performed with a dust blower to allow for optimal concreting.
3.
The pouring of conrete is the next step. The seperation between the concrete slab and the subgrade is achieved due to the placement of the membrane.
As soon as the concrete has reached its required strength, the placement of GSI spring elements follows. Each housing is now equipped with its corresponding spring unit and shims.
5.
Final step will be the lifting of the slab. Our installation team supports you directly on site, with supervising or lifting. A special jack-up device is part of the GSI system and will be used to lift up every single slab. Completion of lift-up procedure results in floating slab track that allows the highest reduction of groundborne vibration and ground-borne noise to the surrounding structure.
- GERB vibration isolation solutions in trackbeds
Implementation
After 10 weeks of construction, the U4 subway line as well as line U2 was put back into service on time. The success of the integrated floating slab track system could be determined by means of subsequent measurements. If you would like to have further information about the implementation or measurements, please contact us.
Share this post
Share this post
Further Resources
You need further information on this topic?
Please do not hesitate to contact us with your individual question.
One of our project engineers will get back to you shortly.
Further Resources
You need further information on this topic?
Please do not hesitate to contact us with your individual question.
One of our project engineers will get back to you shortly.