A series of pullout tests on strip polymer geogrid embedded in dense sandy gravel was carried out and the normal stresses at the soil-reinforcement interface were measured by small earth pressure cells. On basis of these tests, it is found that the restrained positive dilatancy, observed at lower applied normal stresses, results in the increase in actual normal stresses at the soil-reinforcement interface, thereby increasing the pullout resistance of the reinforcement. It is observed that for the strip polymer grid, increase in the normal stresses is the resultant of pullout resistance of transverse members under plane strain conditions plus the edge effect of strip reinforcement under the true three dimensional conditions.
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