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EMBANKMENT TECHNOLOGIES


Managing risk is an integral part of ensuring railway safety, argues Eberhard Groener of Geobrugg AG. S


afety not only in natural hazard miti- gation is an integral issue for railways


in any regard.


In case of an event there is a high risk of damage with substantial extend. Recent natural hazard events in the UK and around the world, possibly boosted by cli- mate change, have highlighted the poten- tial risks to the railway infrastructure from rock fall, shallow landslides and debris fl ows.


The intention of rock fall barriers is to catch individual boulders with a certain ki- netic energy. They have been installed for protection in various places on the UK rail- way infrastructure in recent years where it is uneconomic to stabilise the slopes them- selves.


Approval


Modern fl exible rock fall barriers are read- ily available meeting both Swiss BAFU and European ETAG 27 guidelines, though there are at the moment only a few that fully offi cially comply with the European standard and can carry CE marking. There are some barriers offered which claim to exceed the requirements of ETAG 27 but in fact these only carry university test cer- tifi cates, which are not offi cial European Technical Approvals (ETAs) formally is- sued in accordance with ETAG 27 and therefore the barriers are not in compli- ance with ETAG 27 and cannot have CE marking.


For a high level of safety the European Governmental Body has established the ETAG 27. It is not only for liability rea- sons in regard of performance required to fulfi l these criteria in holding a valid ETA. There are also regular proofs of the production process and the quality of the manufactured materials required to guar- antee the design lifetime. To check whether a rock fall barrier has an offi cial ETA, one


92 | rail technology magazine Jun/Jul 11


should visit www.eota.eu and search the “valid ETAs list” / choose “Number guide- line (xyz)” and type in ETAG 027 next to “Number guideline (xyz)”.


Geobrugg’s GBE barrier range has a num- ber of barriers fully compliant with ETAG 27. The cutting edge technology used was recognised in May 2011 by winning the 2011 Ground Engineering Award for Product Innovation. Beside the product performance in absorbing the kinetic en- ergy, the easy and quick installation was recognised.


In contrast to single rock fall a triggered mass of water, mud and rock comprises an area load to the protection measure. The process of such debris fl ows and shallow landslides is completely different to that of rock fall. Therefore, it is important to ap- preciate the differences between a rock fall event, a landslide event and a debris fl ow event in order to ensure suitable and ad- equate protection for the safety of the trav- elling public and the railway infrastructure.


Landslides


While rock falls tend to have discrete blocks falling at high velocities and debris fl ows tend to be associated with signifi cant water fl ows that erode and entrain soil, shallow landslides generally involve lower volumes of water than debris fl ows and are often triggered by elevated water pressures, usu- ally at the rock/soil interface.


Understanding the behaviour of these event types is the key to the provision of suitable tailored catch fences or barriers that work to deal with the type of hazard effectively and in a cost effective manner. Flexible rock fall barriers have been in common usage for a number of years. The development of fl exible debris fl ow barri- ers is more recent but has reached a point where they may be designed, specifi ed and installed with confi dence. Indeed, installa-


tions are now quite common in European alpine areas, California, Japan and Korea in particular.


The research and development of fl exible landslide barriers is more recent still but is now well advanced with a good under- standing of the behaviour of both the land- slide material and velocities (hence impact pressures) and of the barriers themselves.


Test site


At a landslide test site in Veltheim commu- nity in the Aargau canton of Switzerland, a test slope channel of eight metres wide and 41 metre long with an average inclination of 30° is used to test barriers at full scale by releasing the material down the channel.


A variety of measurements and videos are taken and assessed to validate and improve on the basic design created by computer and fi nite element analysis.


Geobrugg, a Swiss company specialising in debris fl ow mitigation, has been closely in- volved in the research and development of both debris fl ow barriers and more recently landslide barriers and is the world leader in this type of cutting-edge protection system. This means that railway civil and geotech- nical engineers may now specify solutions that can be tailored to each potential type of risk – something that has not been pos- sible until now.


Geobrugg as the market leader tests all its barrier systems in properly controlled full scale tests. They are validated by either of- fi cial government bodies with approvals (rock fall) or independent testing bodies (debris fl ow/shallow landslide) so that cli- ent and consultants may have confi dence that they will perform in real life situations as intended


FOR MORE INFORMATION Visit www.geobrugg.com


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