EFFECTS OF GEOGRID SHEET ON STRENGTH AND STIFFNESS OF LOOSE SAND
H. P. Singh
Associate Professor, Department of Civil Engineering, NERIST, Itanagar, A.P., India
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Reinforced soil is a composite material which is formed by the association of frictional soil and tension resisting elements in the form of sheets, strips, nets, or mats of metal, synthetic fabrics or fiber reinforced plastics and arranged in the soil mass in such a way as to reduce or suppress the tensile strain which might develop under gravity and boundary forces. It is well-known facts that most granular soils are strong in compression and shear but weak in tension. The performance of such soils can be substantially improved by introducing reinforcing elements in the direction of tensile strains in the same way as in reinforced concrete. Keeping this in view the present study was taken up. In this study triaxial compression tests were conducted on a medium dense granular soil (RD = 40 %) reinforced with synthetic geogrid sheet. The geogrid sheets equal to plan dimension of split mould were placed within the triaxial test samples in different combinations such as 3 layers, 4 layers and 5 layers at equal vertical spacing. The stiffness modulus (σd/ÃÂµ) and shear strength parameters (c and ÃÂ) of reinforced sand corresponding to each combination of geogrid sheet were determined in the laboratory. Tests results indicate that the stiffness modulus and the shear strength parameters of soil increase on the inclusion of geogrid sheet. It was also observed that on increasing the number of geogrid sheet these strength parameters further improve and the improvement is substantial corresponding to 5 layers of geogrid sheet. Thus there is a significant improvement in stiffness modulus and shear strength parameters of reinforced soil due to geogrid sheet and the load carrying capacity of reinforced soil will be improved and immediate settlement will be reduced.