Behaviour of Model Square Footing Resting on Sand Reinforced with Three-Dimensional Geogrid

The present investigation proposes a new type of reinforcing material in the form of three-dimensional geogrid. The performance of a model square footing resting on the three-dimensional geogrid reinforced sand bed is investigated by conducting laboratory scaled plate load tests. Two types of 3D geogrids with triangular and rectangular pattern were used. The improvement in bearing capacity and surface deformation were evaluated and the effect of depth of placement of the first layer of reinforcement, the spacing between layers and number of layers were investigated. The results obtained were compared with the results of unreinforced sand bed and conventional geogrid reinforced sand bed. The bearing capacity of the footing was improved by 1.85 times by the provision of a single layer of conventional reinforcement, whereas, 2.7 and 3.1 times improvement was observed with 3D geogrids of the triangular and rectangular pattern at an optimum depth of 0.25B. The results show that the spacing between two consecutive layers varies with the type of reinforcement. Two layers of 3D geogrid (rectangular) at an optimum spacing of 0.75B completely eliminate the surface heave of soil surrounding the footing. In the case of conventional geogrid and 3D geogrid with triangular pattern, the optimum number of reinforcement layer was obtained as four. Three layers of 3D geogrid with rectangular pattern placed at an optimum spacing of 0.75B give a BCR value of 6.4. Also, 3D geogrids perform better than conventional geogrids in reducing surface deformation.