Performance Properties of Geogrids - Reinforced Soil Engineering: Advances in Research and Practice - page 29

Figure 8

Isochronous curves for polypropylene yarn. (From Jewell and Greenwood,

1988.)

Overlaps in the direction of the primary tensile load force were allowed in the
United States, and a special RF joint was used to reduce the design strength of the
geogrid to cover the overall reduction in allowable load due to overlaps. The new
FHWA manual (1997) no longer mentions this method, although it probably will
still be used.

8 SOIL REINFORCEMENT INTERACTION

Failure of a reinforced structure, specifically the reinforcement, can take place in
two ways: tensile rupture of the geogrid or pullout of the grid. These potential
failure modes are assessed separately.
To determine the pullout resistance of a geogrid, mainly pullout tests are
used in which either the coefficient of interaction between the geogrid and soil is
determined or the minimum anchor length is calculated (Voskamp, 1992).
Oostveen et al. (1994) conducted an extensive study of the pullout behavior of
geogrids and executed many tests in a 1000mm by 2000mm pullout box,
comparing extensible geogrids, both stiff and flexible, with nonextensible, steel
grids. This study revealed that the behavior of flexible grids differed completely