Geosynthetics can be used to increase the bearing capacity of poor foundation soils and/or to reduce excessive settlements. This paper analyses the case of shallow foundations on reinforced soil using centrifuge tests, namely that of a strip footing on a horizontal ground reinforced with one layer of geosynthetic. The response of reinforced models was compared to that of a similar unreinforced model. The influence of the depth of the reinforcement layer was studied. Two different reinforcement materials were used: a geotextile and a geogrid. The ultimate bearing capacity, as well as the bearing capacity at particular settlement levels were analysed. The results indicate that using one layer of reinforcement con-tributes to increasing the ultimate bearing capacity, provided the reinforcement is adequately positioned. It is likely that the higher limit for the normalized depth of the reinforcement layer recommended in the literature may need to be reduced, when using only one layer of reinforcement. The improvement in bear-ing capacity at particular settlement levels is important as often the settlement, rather than the bearing ca-pacity, controls design. The models tested exhibited reduced bearing capacity for normalised settlements of 5%B (B, width of the footing), while for smaller normalised settlements (2%B) the reinforcement layer included was effective, particularly when the reinforcement layer was placed nearer to the footing. The experimental data was compared to analytical estimates of the bearing capacity with proposals from the literature. The analytical estimates are optimistic, particularly for the geogrid.
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