Estimation of Dynamic and Liquefaction Properties by Shear Wave Velocity

Abstract

The analysis of foundation vibrations and geotechnical earthquake engineering problems in civil engineering requires characterization of dynamic soil properties using geophysical methods. Dynamic structural analysis of the superstructures also requires knowledge of the dynamic response of the soil­structure, which in turn relies on dynamic soil properties. Geophysical methods are often used to characterize the dynamic soil properties of the subsurface. This method requires a borehole through which a sensing probe is lowered at known level. Source near the borehole is generated artificially with the help of wooden plank and hammer. The seismogram obtained from computer aided system is used to determine shear wave velocity and compressive wave velocity which is further used to calculate dynamic parameters such as Poisson’s ratio, dynamic shear modulus, dynamic elastic modulus and predominant period etc. Ground water table is very close to ground surface and the soil is mainly fine to coarse sand with some intermittent layers of cohesive soils meaning that the soil is very liable to liquefaction. Liquefaction resistance is assessed in terms of cyclic stress ratio and in terms of factor of safety both of which show that the liquefaction potential of the site is very high mainly near shallow depth less than 10m.