Piled Embankement Design: Methods and Case Studies
Embankments on soft subsoil supported by piles or simi lar elements and high-strength geosynthetic reinforce ment on top of them have important advantages com pared to "conventional" embankment foundation: no con solidation time is required, there is no import/export of additional embankment soil to aceeierate consolidation or to compensate the settlement, practically no additional settlement occurs under traffic etc. The application of such solutions is growing recently worldwide. Corresponding design procedures have meantime more than 10 years of history going through significant de velopment, scientific and verification efforts across Europe.
A critical overview of these procedures is presented pointing out the increasing precision and reliability incl. the recent state-of-the-art in Germany. Some typical interesting projects during the last about 10 years are shortly described and discussed including both railroad and road applications, different concepts and geosynthetic reinforcements, measurement programs and experience.
Embankments on piles with geosynthetic reinforcement in the base have reached the stage of maturity. Huge experience is available regarding design procedures, construction and (registered) behaviour.
The range of geosynthetic reinforcements available today and different row materials eliminates any technical Iimitation for their use in such systems. The present experience is that it is financially efficient to maximize pile spacings up to the Iimit of their bearing capacity and to use strenger geosynthetic reinforcement to compensate that.
The recent German design procedures allow to take into account upward Counterpressure from soft subsoil between the piles, thus saves reinforcement costs. Critical issue to be discussed always is: could the latter be lost during 100 years e.g. due to groundwater level sinking.In case of any doubt regarding bearing capacity or serviceability of piled embankments in the stage of design: use stronger reinforcement. The costs are negligible in relation to possible reconstruction costs. Some failed or highly deformed structures are known, but beyond the scope of this paper.