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HUESKER Australia Pty Ltd
PO Box 593
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  • Alexiew, Dr.-Ing. D.
  • Sobolewski, Dr.-Ing. J.
  • Pohlmann, Dipl.-Ing. H.

Projects and Optimized Engineering with Geogrids from 'Non-Usual' Polymers

Abstract

A perfect geosynthetic reinforcement should have from the point of view of geotechnical engineers following  proper­ lies: appropriate  tensile module, low creep, high coefficient of interaction, low installation damage, high chemical resistance, low price. This perfect reinforcement is not available yet. Nevertheless, the use of modern polymers - additionally to the common used PP, PET and HDPE- allows for optimized solutions quite close to the "ideal case". Projects with new geogrids made from aramid and polyvinylalcohol during the last years  are presented and discussed. Three of them are projects with high-strength geogrids from aramid: for overbridging sinkholes at a highway in Germany; to ensure slope stability at a waste disposal in Austria and to reinforce embankment on piles for a new high-speed train in Germany. The projects require high tensile forces at minimized  strains. Further, two projects are reported with geogrids made of polyvinylalcohol: for a waste disposal and for a retaining wall in Germany. In both cases low creep had to be combined  with high alkaline resistance. Typical project cross-sections, the final solutions, characteristic properties ofreinforcement and photos are presented, demonstrating the broaden geotechnical engineers's options today.

Conclusion

The  properties  of  the  geotechnical  engineer's "ideal"  geosynthetic reinforeerneut are described, although no such product ex­ ists as  yet.  However,  present-day  "common" polymers  (high­ tenacity  polyester:  PET,  polyethylene:  PE  and  polypropylene: PP) already  provide some possibility  for optimal choice of rein­ foreerneut products depending on the raw material, because im­ portant properties of reinforeerneut are in fact largely determined by the polymer used.

The  general  advantages  of geogrids  (woven, knitted and extruded) as a reinforeerneut material are explained briefly. Which is more important  (being the focal point ofthe paper): the ongoing  development  of polymers and, based on that, of reneer's scope for project-specific optimisation. In  this  connection,   use  of  the  "latest"   polymers   such  as aramid (AR) and polyvinylalcohol (PVA) has often proved appropriate. In the context  of project  optimisation  there is a brief discus­ sion on properties of these novel polymer geogrids, which are relevant to the engineer, namely modulus, creep behaviour, du­ rability, etc.

The paper includes  recent, more important  projects, in which geogrids in AR and PVA have provided a useful solution, some­ times the only one. Three of these projects involve aramid geogrids in road engi­ neering, landfill construction and railway engineering (including the first use of any kind of aramid geogrid),  and two have used PVA geogrids for landfill and retaining wall construction,  being the firsttime that PVA geogrids have been installed in Germany. Tensile  strengths   of  geogrids  in  the  projects  presented  range from  110 kN/m  to 1200  kN/m  and strains  from about 2.5% to araund 5.0%.

For reasons of space, problems  posed, solutions, characteristic values, experience  and design  methods  have been presented rather briefly, with emphasis on graphic information on project details and reinforeerneut  behaviour. Reference is made to the literature  on the subject, in so far as it is available, given the novelty of the subject matter.

In conclusion it can be said that the above-mentioned applications of novel polymers geogrids noticeably broaden the civil engineer's options for an optimal solutionon  asound base.