Comparison of Penetration Mechanisms of Cone and Spudcan in a Multilayer Deposit with Interbedded Sand Layers-Paper

Paper

Pdf Summary

The study compares cone and spudcan penetration in a four-layer sand–clay–sand–clay deposit using 100g centrifuge tests. Half-scale models were pushed alongside a transparent window, and particle image velocimetry (PIV) tracked soil deformation. Separate full-model tests measured penetration resistance.<br /><br />The cone’s sharp tip produced localized deformation around its tip and did not trap a soil plug. Its resistance responded mainly to the soil immediately around the tip, dropping as it entered clay and rising when it approached sand.<br /><br />The flatter, larger spudcan behaved differently. It accumulated a plug beneath its base, incorporating sand and clay from successive layers, while a sand column formed above it. The plug’s base shifted the effective bearing surface deeper, causing the spudcan to detect underlying layers earlier than the cone. Shear along the plug’s sides also added resistance. Plug size changed through soil backflow and squeezing, particularly near stronger layers.<br /><br />These contrasting mechanisms explain why simple correlations between cone resistance and spudcan resistance can underestimate spudcan resistance in layered soils. The authors conclude that reliable direct design methods must track how the plug’s shape and height evolve and account for its contributions to end bearing and side friction. Correlations developed for uniform soil layers should therefore be applied cautiously to stratified deposits.

Keywords

cone penetration

spudcan penetration

layered soil

sand-clay deposit

centrifuge tests

particle image velocimetry

soil deformation

soil plug

penetration resistance

bearing resistance