Numerical Investigation on the Spudcan Penetration into Sand Overlying Clay Considering the Strain Effects

A numerical model with a Coupled Eulerian–Lagrangian (CEL) approach is proposed for spudcan penetration into sand overlying clay. Both stress-dependence and strain-softening effects are incorporated into the M–C model to describe the sand, whereas the Tresca model with softening effect is used to describe the clay. Effects of the critical state strain threshold in the strain-softening model of sand and the clay sensitivity in the strain-softening model for clay are investigated. The model is verified against different soil conditions: uniform sand, loose sand overlying clay, and dense sand overlying clay. It is found that the stress-dependence effect dominates shallow penetration, whereas the strain-softening effect dominates deep penetration. The assumption of a constant peak friction angle for the accumulated deviatoric plastic strain less than the threshold of peak friction angle leads to an overestimation of the resistance in loose sand. Furthermore, the fit parameter obtained from triaxial tests tends to underestimate the peak resistance in dense sand. The proposed model should provide a valuable tool for geotechnical engineering analysis in sand.