Elastic moduli and porosity profiles in soft soils by using elastic and electromagnetic waves

The void ratio and elastic moduli have been used to understand soil behavior as design parameters in geotechnical engineering. The geophysical method including the elastic and electromagnetic waves has been known as a high resolution technique for evaluating the various subsurface characteristics. The objective of this study is to assess the design parameters such as the void ratio and elastic moduli by using the geophysical method. The probe, called the Field Velocity Resistivity Probe (FVRP), is developed to obtain the elastic and electromagnetic wave profiles based on the geophysical method. The elastic wave velocities such as compressional and shear wave velocities are generated and received by using the Piezoelectric Disk Elements (PDE) and Bender Elements (BE), respectively. The Electrical Resistivity Probe (ERP) is installed at the bottom of the FVRP to obtain the electrical resistivity profile based on the electromagnetic wave. The application test of FVRP is carried out on the southern coast of the Korean peninsula. The penetration tests are performed at a depth of 6∼20 m and the measuring intervals are 10 cm for elastic wave velocities and 0.5cm for electrical resistivity. The void ratios are assessed by using the measured elastic wave velocities and the electrical resistivity. The elastic moduli such as constraint and shear moduli are also calculated through the measured elastic wave velocities. In particular, the void ratios, based on the geophysical method of FVRP, are compared with volumetric void ratios through the standard consolidation test. The comparison shows that the void ratios, based on the FVRP and volume, match well. This study demonstrates that the FVRP may be a useful device to effectively determine the elastic moduli and void ratio in the field.