Random field modeling of CPT data

An extensive set of cone penetration tests (CPT) soundings are analyzed statistically to produce an a priori 1D stochastic soil model for use at other similar sites. The data were collected by the Norwegian Geotechnical Institute at the site of a new airport just north of Oslo, Norway, and consists of 143 CPT soundings over an area of about 18 km(2) in a reasonably homogeneous soil mass. The CPT data consist of cone tip resistance, side friction, and pore-water pressure measurements. Only the cone tip resistance is considered in this study, it beings considered closest to a "point" property of the soil, and only the vertical variation is characterized. To perform the statistical analysis, the data sets are viewed as independent 1D realizations extracted from a statistically homogeneous 3D random field. Plots of various transformations of the data indicate that the cone tip resistance records are best represented using a fractal stochastic model corresponding to so-called fractional Brownian motion, and its parameters are estimated via maximum likelihood.