Practical use of shear wave velocity measurements in UK clays (BGA Touring Lecture 2023)

Abstract

This paper seeks to promote use of shear wave velocity (Vs) measurements in UK clays as a complement to more standard ground investigation techniques. Vs measurements seem to be repeatable and independent of the method of measurement used in isotropic soil conditions – for example, soft clays. However, in glacial tills, and especially in the overconsolidated clays of south-east UK, Vs measurements will differ depending on the direction of propagation and polarisation of the shear waves due to natural stress anisotropy and the fissured nature of the materials. Correlations between Vs and other in situ data and with a variety of soil properties can be very powerful and some have been proposed here for UK clays. However, these correlations should ideally be local and only applied to other soils and areas with great caution. Other uses of the techniques, beyond those of classical dynamic analyses, have been described together with some future challenges. Uncertainties in the methods have been well researched and several methods have been proposed to deal with these uncertainties. Nonetheless, advice from a geophysical colleague will enhance the geotechnical engineers’ use of Vs data.