Empirical relationships of shear wave velocity, SPT-N value and vertical effective stress for different soils in Mashhad, Iran

Abstract

Shear wave velocity, V s, is one of the important input parameters in seismic response analysis of the ground. Various methods have been examined 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 Vs 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.