Performance Properties of Geogrids - Reinforced Soil Engineering: Advances in Research and Practice - page 30

Figure 9 Isochronous curves for polyethylene grid. (From Jewell and Greenwood,

1988.)

from that of steel grids, with regard to the load transfer between the grid and
surrounding soil.
Unlike stiff, nondeformable steel mesh, extensible geogrids do not have a
constant load transfer by shear. This also means that the coefficient of interaction
is not a constant value. The total anchor length required, however, is no more than
that calculated with a constant value for the coefficient of interaction. Further
research is being conducted. Whichever method is chosen, pullout or maximum
anchor length, the load is transferred by the maximum mobilized number of
junctions in the anchor zone, e.g., anchor length multiplied by the width.
Not once during the pullout tests that were executed on flexible geogrids,
Fortrac, under various test conditions and with various fill materials was a
junction failure observed. This proves that the junction strength under confined
conditions is always sufficiently high.
If an anchor length of 1 m is assumed, the number of junctions over this
length is approximately 1600 if 40 rib junctions occur over 1.00 m. As the load is
always transferred over a certain anchor length, the requirement of a high
junction strength, sometimes specified as 90%, is not necessary. Such a
requirement is clearly biased as it strongly favors monolithic junctions. The only