Shear wave velocity, V_s, is one of the important input parameters in seismic response analysis of the ground. Various methods have been attempted to measure the soil V_s directly. Direct measurement of V_s is time consuming and costly, therefore many researchers have been trying to update empirical relationships between Vs and other geotechnical properties of soils such as SPT Blow count, SPT-N. In this study the existence of a statistical relationship between V_s, 〖SPT-N〗_60 and vertical effective stress, σ_v', is investigated. Data set we used in this study was gathered from geotechnical and geophysical investigations reports. The data have been extracted from more than 130 numbers of geotechnical boreholes from different parts of Mashhad city. In each borehole the V_s has been measured by downhole method at two meter intervals. The SPT test also has performed at the same depth. Finally relationships were developed by regression analysis for gravels, sands and fine grain soils. The proposed relationships indicate that V_s is strongly dependent on σ_v'. In this paper the effect of fine percent also is considered on the V_s estimation.

Keywords