Effect of saturation and plasticity on dynamic properties of silt

Resonant column and torsional simple shear tests were conducted on Mid Missouri silt to study the effect of saturation and plasticity on the dynamic shear modulus and damping. Tests were performed on reconstituted soil samples prepared at different degrees of saturation and plasticity indices. The degree of saturation was found to influence the shear modulus significantly at low strains due to capillary stresses. The maximum influence occurred at particular degree of saturation which was found to be 18.8 percent for the soil tested. The shear modulus was observed to degrade more rapidly with strain amplitude as the saturation is increased. Damping was found to be less for samples with higher degree of saturation but increases at a higher rate with the strain amplitude. The study showed that an increase in plasticity index increased the low amplitude shear modulus but the modulus degraded more with increasing strain amplitude. Consequently at high strains, samples with relatively less plasticity had higher modulus values. The Effect of plasticity on damping was not so distinct. The only information extracted was that samples with plasticity indices 6.8 and 17.1 percent showed higher damping ratio than samples with zero plasticity index --Abstract, page iii