Wheel loading on a paved or un-paved surface is effectively plate loading that generates a cone of radial stresses within the engineering fill below the surface and at the interface of this fill with the prepared subgrade or natural ground. When the fill is reinforced by one or more geogrids the radial, horizontal components of these stresses are resisted by radial tension in each geogrid layer. When all geogrids had square or rectangular apertures, information relevant to the ability of the geogrid to carry these radial stresses could be derived from tensile testing in the two principal directions of the geogrid. However, this does not apply to newer geogrids with triangular apertures. Instead, it has been proposed that uniaxial testing in multiple directions around 360° should be used for both these newer geogrids and also square/rectangular aperture geogrids to compare their potentials under radial loading. The authors of this paper believe that such testing is inappropriate. To study how best to represent radial load uptake by all geogrids, regardless of aperture shape, a new test has been developed that measures the average radial tension in a geogrid sample that is subjected to radial strain at a low level. The development of this test has been reported at various conferences over the past six years. Reported at GeoFrontiers 2011, initial results from use of this new test suggested that the results compared well to a simple mathematical derivation of the response of a geogrid to radial strain based on a geogrid’s single rib tensile load-strain properties. Further testing has now confirmed this relationship and demonstrated that the previous concept of using uniaxial testing at various angles is not relevant to this loading condition. This conclusion has now been confirmed by full-scale field tests reported at 10ICG in 2014 and further reported here.
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