Soil Classification using Shear Wave Velocity in Shiraz City based on Building Codes

Seismic site characterization studies are carried out in earthquake- prone areas. In these studies seismic design parameters are chosen based on engineering geological and geotechnical characteristics of the site. Site classification is addressed in various building codes. Codes define various methods for soil classification such as measurement of average shear wave velocity up to 30 meters depth. This paper present a part of the seismic geotechnical microzonation study of Shiraz city based on seismic data for soil classification. This method, measures the travel times of multiple elastic waves along the interface of layers having different velocities. In this study a seismograph with an array of 24 geophones and 3.75m intervals was used. The shear wave velocity distribution estimated for 3 different seismic layers. S ismic bedrock was defined as layer for which shear wave velocity is more than 750 m/s. Depth of seismic bedrock was estimated to vary about 1 to 29m.The average shear wave velocity up to depth of 30 m ranges about 375 to 1253m/s. Based on the results soil profile in Shiraz were classified and compared with the Standard No. 2800 and Eurocode-08. The result indicated that Shiraz city can be placed in “site class I” and “site class B, E and A” respectively.The study revealed that Standard No. 2800 site classification should be modified.