BEHAVIOUR OF GEOGRID-REINFORCED SAND BEDS

Soft clays and loose sand beds pose the problems of poor bearing capacity and detrimental settlements. As a result, structures founded in these soils are subjected to distress and instability. Various ground improvement techniques have been devised for improving the bearing capacity and reducing settlements of these types of soils. Vibro compaction, stone columns, preloading with sand drains, chemical stabilization, lime soil piles and grouting have been some of the successful ground improvement techniques which the geotechnical engineers the world over have adopted in the profession. Reinforced earth is also one of very effective techniques to improve bearing capacity. Recently geosynthetic reinforcement of ground has been found as an important development in reinforced earth. Geotextiles, geofabrics and geogrids have been the reinforcement components used for improving bearing capacity of poor soils. In this thesis a high density polyethylene geogrid has been used as horizontal reinforcement in a loose sand bed to improve its bearing capacity. A series of laboratory model tests was conducted to study the improvement in bearing capacity of fine sand, medium sand and coarse sand, all compacted to a relative density of 50%. A surface footing plate of diameter 60 mm was used as the shallow foundation. Circular geogrids of diameter 120 mm were used as reinforcement layers. The number of geogrids and the spacing between them were varied in the study. It was found that the horizontal geogrid reinforcement improved the bearing capacity of the loose sand layer. Bearing capacity was found to improve further with increase in number of geogrid layers and with decrease in spacing between them