Estimation of the porosity of clay soils using seismic P- and S-wave velocities

Abstract

Seismic waves are commonly used to investigate how the soils behave during the earthquake. The goal of this study is to predict the porosity of shallow clay soils from seismic wave velocities investigated the dynamic properties of the soil and to develop the porosity graphs depending on geotechnical properties of the soils. The parameters used to determine porosity are compressional (P) and shear (S) wave velocities, seismic velocity ratio, Poisson ratio, bulk modulus, shear modulus. This study calculates bulk modulus, shear modulus and Poisson ratio from P- and S-wave velocities obtained by using the seismic-refraction method, and porosity values using grain and dry densities of core samples obtained from several boreholes within the study area. The study area is located in western Turkey, and has predominantly clay-silt-sand-gravel deposits. The data of the clay soils within the area were separately arranged based on the values of the Poisson ratio, seismic P wave velocity, seismic velocity ratio (Vp/Vs) and the stiffness of the clay soils. Using these parameters, new multi-parameter relationships were established among shear modulus, Poisson ratio, seismic velocities and porosity of clay soils. The errors of the parameters used for each relationship were determined using the error norm technique. According to the results of the error norm technique, the shear wave velocity and shear module have lowest error for estimating porosity. Consequently, the proposed relationships are recommended to estimate porosity of shallow clay soils. These relationships, in addition to estimate the porosity of clay soil, can be interpreted whether the liquid and/or gas saturation of pores of this soil. Also, the experimental results show that if the ratio of Vp/Vs < 1.53, the pores spaces of the clay soil are filled with gas.