PERFORMANCE OF THREE FOOTINGS ON REINFORCED SAND

Bearing capacity of soil plays an important role in design of foundations. Considering the amount of bearing capacity more than the actual can cause severe damage to the structures. On the other hand, underestimating the bearing capacity makes the foundation uneconomical. The general scenario is to design the footings as an isolated footing. The interfering as well as spacing effect is not considered while designing the footings. Interference occurs when a number of closely spaced footings are constructed. This occurrence has a significant effect on the ultimate bearing capacity, settlement, tilt and the failure mechanism of the footings. In the present study, the influence of three adjoining square surface footings in series on bearing capacity and settlement resting on reinforced and unreinforced sand were investigated. The parameters include effect of reinforcement configurations (Depth of first layer geogrid reinforcement (u) and Vertical distance between geogrid reinforcement layers (h)) and center to center distance between three footings. In order to evaluate this effects laboratory model tests were conducted at 55% relative density of sand for simulating the various conditions of footing. For reinforced sand three geogrid layers of equal length was used. The bearing capacity and settlement of adjacent footings has been observed to be improved by providing continuous geogrid reinforcement layer in the foundation soil under the closely spaced footings. It was observed that the layout of reinforcement play a vital role in bearing capacity improvement. The optimum depth of first layer geogrid reinforcement is 0.3 times the width of the footing (u/B=0.3) and the optimum vertical distance between geogrid reinforcing layers is also 0.3 times the width of the footing (h/B=0.3).