Cavity Expansion Analysis for CPT in Granular Soils at Small Gravity Fields

Abstract

Cone penetration test (CPT) is a widely used and versatile in-situ tool for determination of soil properties and delineation of soil stratigraphy, which could also act as a useful device for the site characterization of surface soils of other planets during deep space exploration. An analytical solution of drained spherical/cylindrical cavity expansion is developed using a simple non-associated flow model for sand, with consideration of small gravitational environments. The soil model adopted a family of yield loci for triaxial compression based on the normality criterion and a simple stress-dilatancy rule, which showed the ability to model many behaviors of isotropically consolidated clays and sands. The large strains for soil in the plastic region are assumed in this solution, together with the approach of auxiliary variable to convert the Eulerian formulation to the Lagrangian description. The proposed solution is validated against the numerical results for the recovered Cam-clay model. The interpretation of CPT data is then analyzed by this proposed cavity expansion analysis, through the correlation between the cone tip resistance and the calculated cavity pressure. In order to investigate effects of gravity on planets like moon, a simplified approach of normalization is adopted for the analysis of penetration resistance. The predictions of normalised penetration resistance provide good comparisons with previous experimental and numerical results, which indicates the effectiveness of the proposed method for analysis of CPT data under various gravitational environments.