Evaluation of the scale of fluctuation of geotechnical parameters by autocorrelation function and semivariogram function

•Use of semivariogram function to determine the Scale of fluctuation of real data.•Use of Autocorrelation function to determine the Scale of fluctuation of real data.•Examination of relationships between the SOF computed by ACF and SVF.

The spatial variability of geotechnical parameters is determined in terms of their scale of fluctuation (SOF), θ. There are basically two approaches in analyzing the spatial variability of geotechnical parameters in order to determine their SOF. One uses an autocorrelation function (ACF) from random field theory and time series analysis and the other uses the semivariogram function (SVF) from geostatistics. Most of the published data on the spatial variability of geotechnical parameters were obtained using these methods, other methods include the local average theory and maximum likelihood method were also commonly adopted in the literature. The SOF, however, is not an inherent geotechnical property. Hence the SOF of a geotechnical parameter is dependent on factors such as geological setting, testing, and estimation methods among others. Since SOF is a non-inherent geotechnical property, it is expected that the SOF computed using different methods will give different values. Based on seven CPTu borings on predominantly soft clay in Hayti, Pemiscot County, Missouri, this paper presents an evaluation of the SOF estimated using both the ACF and the SVF with a view to determining the presence of any patterns to the difference and correlations between the two methods.