Geophysical method for geotechnics case studies: Standard penetration test and rock quality designation

Geophysical methods are powerful tools to explore site characterization for geotechnics. Among the possible fields of geophysical application are hydrocarbon, mineral and geothermal exploration, disaster mitigation, environmental, slope stability assessments, soil characterization and searching of an archaeological site. The available techniques are characterized by different penetration and resolution capabilities, from a few centimetres to kilometres. This paper presents an original use of Spectral Analysis of Surface Wave (SASW) method to site characterization of soil stiffness, and it will be compared with Standard Penetration Test (SPT), and for rock mass strength identification it will be compared with Rock Quality Designation (RQD). Surface wave dispersion analysis is widely used in geophysics to infer a shear wave velocity model of the subsoil for a wide variety of application (Foti, S. et al., 2011) and to suppose strength of rock mass for RQD parameter estimation. Objectives of the paper are, first to the point that SASW method is an insitu tests, rapid and cost-effective geotechnical investigation, second to show that application of SASW method in the subsoil and rock mass can provide accurate parameters of N-SPT for soil stiffness and RQD for rock mass strength. Finally, some illustrations of the advantages or disadvantages and compare the result of the SASW method with the conventional geotechnical test are presented.