EVALUATION OF LIQUEFACTION POTENTIAL OF SATURATED SANDS

Abstract

The failure of the Civil Engineering structures occur during on Earthquake due to various- reasons amongst which liquefaction is one. The structure resting on loose saturated sand deposit is most vulnerable to damage or destruction. Careful consideration of the stability of structure against the phenomenon Liquefaction is central to good engineering practices, and there now exist a large body of knowledge concerning the various parameters and variables which are important to a clear understanding of the processes affecting the stability. Many of the accepted and popular methods are applicable for evaluation of liquefaction potential of saturated sand. It is desirable to consider and understand significant factors relevant to liquefaction. The liquefaction potential of a site, i.e. whether the liquefaction would occur at a site depends mainly on, (1) the intensity of shaking, i.e. the magnitude of acceleration of a site and duration of the earthquake stress pulses, (2) the relative density of the soil deposit, (3) overburden pressures at the level considered and, (4) the soil particle size. The important approaches utilizing these factors are given by, (1) Seed and Idriss (1970), (2) Chinese Building code (1974) and, (3) Japanese State-of-the-Ai't (Iwasaki, 1986). In the work herein these approaches have been studied for utilization of the above mentioned parameters with regard to their relative weightages. For this purpose software has been prepared for the three approaches and plots have been obtained for a number of numerical values for these parameters. On the basis of these study it has been inferred that the stress ratio causing liquefaction works out to be more in Japanese approach. The cyclic strength ratio as obtained by Seed and Idriss approach are lower in comparison to that from Japanese approach