Analysis of potential liquefaction depending on shear-wave velocity

Prediction of soil liquefaction resistance in earthquake-prone regions is an important step in retrofit of existing structures and engineering design of new buildings. In the late 1960s H.B. Seed and I.M. Idriss developed a simplified procedure for evaluation of soil liquefaction resistance from Niigata and Alaska earthquakes in 1964. This procedure which is based on Standard Penetration Test has become a standard in many countries around the world. Shear wave velocity measurements provide either an alternative or a supplement to this approach. In this thesis, cyclic stress ratio causing liquefaction was determined by using shear wave velocity measurements and dominant periods of earthquake waves. It was shown that there is compatibility between this ratio and the ratio developed by H.B. Seed and I.M. Idriss. Liquefaction resistance curves were established by application of an ampirical relationship between the cyclic stress ratio for cyclic shear deformation proposed by R. Dobry and the shear wave velocity. This procedure, which is established using the cyclic stress ratio, shear wave velocity and liquefaction resistance curves follows the general form of the penetration-based simplified procedure. The proposed procedure was cornfirrned by case history data by various researchers from 24 earthquakes and measurement sites in soils ranging from clean fine sand to sandy gravel to profiles including silty clay layers. This procedure correctly predicts liquefaction potential for 98% of the liquefaction case histories. Additionally it is shown that this is compatible with the standard penetration blow count based liquefaction analysis results proposed by Youd and 20 other researchers. Furthermore, liquefaction resistance curve of the proposed procedure is compatible with various liquefaction resistance curves determined by Andrus and Stokoe in 1997 and 2000.To improve the validity of the proposed procedure, additional case histories are required with all soil types that have and have not liquefied, especially deeper deposites (zad>10m.) and from denser soils (Vs>250) shaken by stronger earthquakes ( Zma^OASg). This procedure, while providing practice in potential liquefaction evaluation of soils, can be used as a resource document for researchers. Keywords : Liquefaction, Shear Wave Velocity, Shear Stress Ratio, Liquefaction Resistance Curves, Dominant Periods of Earthquake Waves, Acceleration.