EFFECT OF SAMPLE PREPARATION METHODS ON SHEAR WAVE VELOCITY

Shear wave velocily, Vs, or low amplitude shear modulus Go, is one of the most important soil properties which is used for predicting dynamic response of soils. Although studies on initial shear modulus have been started from about three decades ago by employing resonant column test and later cyclic triaxial devices, the effects of some factors such as fabric on Vs have not yet been fully studied. Many studies have shown that a given cohesionless soil may have different fabrics at the same void ratio or relative density. Characterization of the fabric of a cohesionless soil can be done in terms of grain shape factors, grain orientation and interparticle orientations. While the effect of grain shape has been well known, only in the early ۱۹۷۰'s attention was directed to study on particle arrangements in cohesionless soils (Oda, ۱۹۷۲, Mahmood and Mitchell, ۱۹۷۴, Oda, ۱۹۷۵, Mitchell et al. ۱۹۷۶). These works showed that characterization of the properties of sands and gravels cannot be done only in terms of density or relative density, as had previously been thought, and effect of fabric and soil structure must be considered in these materials as well. The effect of different fabric produced during different sample preparation methods are discused in this paper. Results of Vs measurement tesi conducted on specimens of Toyoura sand prepared in three different sample preparation methods are presented and compared with the other empirical formulas. Based on experimental results a new empirical formulas is presented.