Abstract
The field measurement of shear wave velocity (Vs) is essential for geotechnical design practices, as it directly provides the initial tangent shear modulus at very small strain levels (γs < 10-6) in geo-materials. The small strain shear stiffness is a fundamental soil property for assessing dynamic loading responses, ground vibrations, and static deformation problems related to shallow and deep foundations. In addition, the Vs is one of the critical elements in evaluating seismic ground hazards such as site amplification and liquefaction potential. Various field and laboratory geotechnical site investigation programs in Kazakhstan have been conducted to understand basic soil behavior. However, in-situ geophysical seismic surveys such as surface reflection and refraction tests and down-hole and cross-hole tests were generally not included in the site investigation program in Kazakhstan, and a few limited seismic surveys have been carried out for specific projects. In most prior construction projects, the small strain shear stiffness was assessed by limited data using general empirical correlations from other in-situ measurements or selective laboratory testing programs that may result in significant uncertainties. In this study, in-situ dynamic soil characteristics of loam soils using active MASW (multi-channel analysis of surface waves) testing are evaluated to obtain comprehensive insights for geotechnical boundary value problems. The resulting Vs profiles are in good agreement with a-priory known geotechnical information (e.g., borehole logs) of sites. Thus, to minimize potential uncertainties of dynamic soil properties estimation via in-situ tests, MASW methods are suggested for construction works in Kazakhstan.