Bearing pressure enhancement of sand foundation beds by encapsulating geogrids in thin densified gravel layer inclusions

This paper presents a novel experimental investigation for improving the bearing pressure resistance of medium-dense sand deposits. Model footing tests were performed on similarly prepared sand beds to examine the effects of incorporating one, two and three separate geogrid-reinforced thin densified gravel layers at various depths within the beds. Additional load tests investigated incorporating only geogrid-reinforcement layers or densified gravel layers of different thicknesses placed separately within the sand beds for the purposes of establishing their resistance contributions. Furthermore, a dimensional analysis relating the model test results to the large-scale conditions is presented. Compared to the unreinforced medium-dense sand bed, superior bearing-pressure resistances (and reduced footing settlements) were achieved for including the geogrid-reinforced gravel layers. For example, at a settlement ratio of 2% (s/D = 2%), the inclusion of one, two, and three geogrid-reinforced thin densified SwG layers improved performance by 68%, 110%, and 124%, respectively, compared to the unreinforced sand bed. Increasing the number of these layers (from one to three) produced improved geomechanical performance, albeit more layers produced diminishing returns. The basic mechanisms responsible for the improvements in bearing pressure resistance are elucidated. This study demonstrates that when suitable engineering fill is unavailable, the concept of incorporating geogrid reinforced thin densified granular layers in the backfill could be of practical application for constructing reinforced footings, reinforced soil walls, etc.