Correlations between resistivity and seismic velocities depending on physical properties of different grain size soils

Parameters obtained from geophysical methods depending on the physical features of the soil are differently affected. Therefore, one method may be preferable according to the other. In literature, relationships have existed between parameters obtained from shallow seismic refraction and direct current resistivity methods. Using these relationships are provided to each other transformations of the geotechnical parameters. However, only one soil type or only P wave velocity was used in these relationships. Besides, it seems that the saturation type (liquid or gas) of the soil is not taken into account in these relationships.

In this study, relationships between seismic compressional and shear wave velocities (Vp, Vs) and resistivity (R) were developed by taking into account the soil type and the saturation type of the soil. The data used in these relationships were classified according to the type of soil (clay+silt, sand, or gravel) and whether the soil was wet or dry. Relationships between P and S wave velocities and resistivity values based on the classified data were investigated. Accordingly, new empirical relationships were determined to estimate the P and S wave velocities from resistivity values with RMSE of 0.22 km/s and 0.06 km/s, respectively. In these relationships, the resistivity limit values (R_limit) between wet and dry data were found to be 18.5 Ω.m, 57.5 Ω.m, and 99.5 Ω.m for silt + clay, sand, and gravel soils respectively. The degrees of saturation (Sr) of the clay+silt, sand, and gravel soil were estimated by using the seismic velocities obtained from these relationships and field studies. The obtained results were compared and RMSE were obtained as 0.17, 0.16, and 0.16 for clay+silt, sand, and gravel soil, respectively.