Characteristics of Bearing Capacity for Single and Two Layer Soil Reinforced with Geogrid

A series of model tests was performed for behaviour characteristics of the shallow foundation on sand and sand-clay using the geogrid-reinforced members. The relative density of soil war made to be 55%, 65%, 75% using raining method and the intervals of geogrid placement was increased by 0.25, 0.333, 0.5 times of the foundation width, respectively. The ultimate bearing capacity of shallow foundation on sand was determined by observing the foundation behaviour to failure with the variation of relative density, intervals of geogrid placement, and length of reinforced members. To evaluate the reinforcing effect of geogrid and the ultimate bearing capacity in sand-clay foundation, the experiment was performed with variation of thickness of upper sand layer and the length of reinforcement. As a results of model tests, average bearing capacity was increased by four times in case of relative density 55% and by three times in case of relative density 75%, indicating higher reinforcing effect at low sand density than at high density. In the sand-soft clay reinforced to by geogrid, reinforcing effect does not increase. Therefore, it propose that the thickness of sand layer that can get maximum reinforcing effect must be over 0.6 times(H/B=0.6) of foundation width and the length of reinforced member must be 6 times of it.