This paper presents the results of a series of large scale direct shear tests carried out using sand and geogrid to appraise the contribution of shear resistance at interfaces between soil-soil, soil-geogrid and the soil- transverse ribs of a geogrid during the test.Soil samples used are with varying proportions of Sand, 6mm aggregates and 12mm aggregates at different densities. The study results revealed that the transverse ribs contribute 17% of the total interface resistance for soil samples

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... tested with the geogrid. From the test results it is observed that the shear strength at sand - geogrid interface mobilized under direct shear mode is depending on thedensity, size of the particles and thickness of ribs. Moreover, it is observed that the passive resistance contributed by ribs found decreasing with increase of normal load and the passive resistance found decreasing with decreasing of density.