Large sample spacing in evaluation of vertical strength variability of clayey soil

The effects of large sample spacing associated with evaluating the vertical strength variability of a clayey soil are discussed in this paper. The research concerns 0.2 m sample spaced cone penetration data profiles analyzed by means of statistical treatment. The aim is to verify the effects of this sample spacing, or that greater than 0.2 m, on trend definition and on parameters which describe the vertical strength variability of the soil. We consider the variance and the scale of fluctuation of the strength values compared to the trend. This investigation also involves the effects of large sample spacing on the location of geostatistical boundaries and the importance of the trend removal technique for obtaining a sound set of residuals. The results of this research provide both theoretical indications and engineering prescriptions for planning a site characterization program.