Apparently your term is the same as a bloque tecnico. I don't know whether you speak French, but this was the conclusion reached by a translator from Spanish into French:

http://forum.wordreference.com/showthread.php?t=1199598

http://www.proz.com/kudoz/spanish_to_french/construction_civ...

Please see this ref, as it has some diagrams:

http://www.atc-piarc.com/media/jornadas_files/17.pdf?PHPSESS...

These links should say that they are the same (but I have been interrupted in the middle of answering this and have lost the flow, so-to-speak):

http://www.atc-piarc.com/media/jornadas_files/20.pdf?PHPSESS...


http://www.ciccp.es/ImgWeb/Sede Nacional/Cursos 2005-06/curs...

Here are some photos:

http://www.cedex.es/castellano/actividades/datos/memoria2004...

of course, technical block googles as badly in English as transition wedge does, transition block doesn't fare much better, but I have very little time left to search, so I hope this will point you in the right direction.

This is the abstract of a paper translated from Spanish, but I hope it gives you an idea of what I think is involved here:

Abstract

The experience of several European railway systems has shown that problems occur frequently in zones with embankment–structure transitions, and these areas therefore require repeated maintenance. To date, no adequate solution for these zones has been demonstrated, and different European railway systems have adopted different design approaches.

In this work, a finite-element model is developed to simulate the behaviour of embankment–structure transitions to improve the methods available for modelling railway track designs. The most distinctive characteristic of the model proposed here is its attempt to simulate the real behaviour of the diverse materials that make up the structure of the track in a transition. To achieve this, a three-dimensional model with boundary conditions that more closely resemble real conditions was used; the model assumes that the surface defining the embankment slope is free and it takes into account the elastoplastic behaviour of the soil.

This model was tested by numerical calculations of several case studies created from different values of geotechnical and geometrical parameters of transition zones. The results from this analysis will help to define new criteria for improving the design of embankment–structure transitions.
http://journals.pepublishing.com/content/f4r2341241u37w43/



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Note added at 14 hrs (2009-06-10 09:42:01 GMT)
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Para minimizar los efectos negativos sobre la vía y sobre las circulaciones, el ferrocarril se plantea la realización de bloques técnicos (denominación de origen francés) o cuñas de transición en la denominación española.

http://www.atc-piarc.com/media/jornadas_files/24.pdf?PHPSESS...

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Note added at 14 hrs (2009-06-10 09:54:36 GMT)
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This dicitonary link translate bloc technique as technical unit (which doesn't google well either)

http://books.google.co.uk/books?id=tWvOUz1QiAAC&pg=PA1311&lp...

I've also tried transition unit/element, but no really relevant hits for them either.

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Note added at 15 hrs (2009-06-10 10:43:08 GMT)
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Here I have found transition segment:

http://books.google.co.uk/books?id=ogSVy9TbmbMC&pg=PA265&lpg...

Here are some good diagrams:

http://www.sustainablebridges.net/main.php/12_Inspection of ...

More info in this book ref here:

http://books.google.co.uk/books?id=NQ48-fTxisYC&pg=PA348&lpg...

Finally, transition structure gets some relevant hits:

http://jshce.com/files/CaseHist5_2004_CATltwtfills.pdf

http://www.azdot.gov/Highways/bridge/Guidelines/DesignGuidel...