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EURO RAIL EXPERTISE


One of the biggest challenges in Europe today is the retrofitting of the rail infrastructure, especially tunnels, whilst still maintaining a service. Stefan Knittel, managing director of Rhomberg Rail Austria, explains how larger trains and an increase in line- side material has forced a rethink on how this work is carried out.


M


any of our major European tunnels were constructed over 100 years ago,


and are in need of renovation. Often these busy lines have reached their capacity lim- its, creating bottlenecks in trans-European commerce.


The same can also be said for city metro lines; many were built over 100 years ago – in London some are over 150 years old – but they cannot be closed for long periods due to the massive disturbances to the city they serve.


We at Rhomberg have faced this ‘renova- tion under operation’ question and started our process considering the tunnel condi- tions. We realise that records were, by to- day’s standards, poorly kept, or are now lost. We therefore need to go back to basics. Old tunnels often have inner shells built without anchoring, just by lining up stones and bricks to tunnel arches to sustain the rock pressure and possible deformations.


The form, thickness and extent of the bricking change over the length of a tunnel, depending on the rock conditions that the original tunnellers faced. In many cases, pressures in the bottom area of the tunnels were assumed for different rolling stock with very different performance levels.


Rhomberg strongly feel that surveys of actual conditions are paramount, even if it takes longer, since far more time can be saved in the construction phase of the project.


These surveys also highlight other difficulties found in old tunnels: fragile and damaged rock and brickwork structures; the quality of the original brickwork; and hidden cavities behind the brickwork from decades of operation and ground movement.


And once these problems have been as- certained, the working conditions in the


tunnels will need to be assessed, which include: limited access time due to service requirements; the distance from tunnel access to site; the difficulty of transport- ing material to site; free space in which to work; ensuring the tunnel is fit for opera- tion at the end of the possession; and that material storage can’t be at the work site and often the space for storage off-site in major cities is also at a premium.


Rhomberg believes that the number of so- lutions is limited, but by keeping the fol- lowing topics in mind over the complete project lifecycle and by using a mechanised rail-bound solution, we can overcome these issues, successfully, for both our cli- ents and ourselves:


• A safe working environment for staff and visitors: ensure that separation from train movements is complete, that dust and dirt are kept to a minimum – a 100-year-old tunnel may have 60 years


52 | rail technology magazine Jun/Jul 11


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