Geotechnical and Geological Engineering, 1994, 12, 133-141 TECHNICAL NOTE The effects of foundation width on model tests for the bearing capacity of sand with geogrid reinforcement B.M. DAS* and M.T. OMAR Southern Illinois University, Carbondale, Illinois 62901, USA Received 7 September 1993 Summary Laboratory model test results for the ultimate bearing capacity of surface strip foundations on geogrid-reinforced sand and unreinforced sand are presented. A fine uniform sand and one type of geogrid (Tensar BX1000(SSO)) were used for the tests. The width of the foundation and the relative density of sand were varied to determine their effects on the bearing capacity ratio. It was found that the bearing capacity ratio of the sand-geogrid system decreased with an increase in foundation width. However, above a certain foundation width (130-140 mm) a practically constant value of bearing capacity ratio was observed. Keywords: Bearing capacity, bearing capacity ratio, geogrid reinforcement, model test. Introduction Recently, several laboratory bearing capacity test results on small-scale model foundations supported by geogrid-reinforced sand have been published (Guido et al., 1986; Khing et al., 1992; Omar et al., 1993; Yeo et al., 1993). The tests were conducted by reinforcing sand with several layers of geogrid (as shown in Fig. 1) in order to determine the critical depth ratio [(d/B)cr] and the critical width ratio [(b/B)cr] of the geogrid layers for mobilization of the maximum bearing capacity ratio (BCR) for a given sand-geogrid system. The bearing capacity ratio is defined as BCR - qu(R) (1) qu where qu(R) and qu = the ultimate bearing capacity, respectively, with and without geogrid reinforcement. *To whom correspondence should be addressed. 0960-3182 9 1994 Chapman & Hall