EFFECT OF SATURATION ON DYNAMIC SOIL PROPERTIES IN LOW STRAIN RANGE

Abstract

Dynamic soil properties will govern the behaviour of samples of sand when subjected to any dynamic loadings. The major dynamic properties are shear modulus (G), damping ratio (D), elastic modulus (E), and Poisson’s ratio (ν). These values are dependent on strain levels and confining pressure. Degree of saturation has significant impact on these properties, as they have effect of water content. There are various tests available to determine these properties. The tests can be done in high strain range and in low strain range. Resonant column apparatus is used for determining the properties in low strain range ( to )%. The apparatus will be in fixed free condition and the driving system allows the specimen to be subjected to fundamental modes of vibration both in torsion as well as in flexure. These tests are performed on Solani sand to determine the properties. Present study was carried out on samples of size 50 mm diameter and 100mm height. The tests are done on relative densities (30 %, 50%, and 70%) and confining pressures (50 kPa, 100 kPa and 200 kPa). The tests with inclusion of fibres are done at relative density (30%, 50%) and confining pressure (50 kPa and 100 kPa) and its effect of saturation is determined. The fiber considered was 0.75% by weight. The tests are done on fibres to make the soil more resistant. It was observed that the shear modulus of saturated sample is smaller than that of dry sample. The modulus of elasticity of saturated specimen is also smaller than that of saturated specimen. The damping ratio for saturated specimen is greater than that of dry specimen. The Poisson’s ratio is more for saturated specimen as compared to dry specimen. The Poisson’s ratio value increases with increase in confining pressure. Inclusion of fiber increases shear modulus and modulus of elasticity and decreases damping ratio. Further shear modulus is smaller for saturated sample than that for dry samples. However for damping ratios it is reverse.