Shear wave velocity as a tool for characterising undrained shear strength of Nordic clays

Abstract

There has been increasing recent use of shear wave velocity (Vs) measurements in geotechnical engineering practice. This has been driven by advances in cost effective and efficient methods of determination of Vs. Traditionally Vs measurements were used for seismic hazard assessment or dynamic analyses. However, they are being increasingly used for general site characterization studies, determination of strength and compressibility parameters by empirical correlation, assessment of sample disturbance effects and in the quality control of ground improvement schemes. This paper will briefly present the methods used to determine Vs and give some examples of Vs measurements in clays from Finland, Norway and Sweden. Despite similar depositional environments the range of Vs profiles for these three countries is significantly different. Differences in the profiles appear to be consistent with differences in basic clay properties, e.g. water content, density or plasticity. Nevertheless, the relationship between Vs and undrained shear strength (su) of clays appears to follow a similar trend for clays from Sweden, Finland and Norway. Correlations between Vs and su exist in the literature for Norwegian clays based on DSS tests. This paper studies the relationship between Vs and su from field vane test, which is commonly used in Finnish geotechnical practice. The proposed correlation is based on data from Sweden and Finland and is meant to be used for preliminary estimate of su from Vs in absence of test data or for validation of available test data.