Simplified numerical prediction of the penetration resistance profile of spudcan foundation on sediments with interbedded medium-loose sand layer

• A simplified method, in which no more strain softening parameters are required as input data, is presented to numerically predict the penetration resistance profile of spudcan in sediments with interbedded medium-loose sand overlying clay layer.
• The full penetration resistance profile is predicted in three steps through the simplified method. By comparison with the centrifuge tests data as well as the field records, good performance of the simplified method is exhibited for the interbedded medium-loose sand layer.

In strong-over-soft strata, there is a potential for an installing spudcan to experience a punch-through failure, where the spudcan would penetrate a certain distance at a short time after the peak penetration resistance. Such a sudden punch-through failure would seriously threaten safety of the offshore structures, even causing casualties. This paper reports results from numerical modeling of spudcan penetration in sediments with interbedded medium-loose sand overlying a clay layer. Three typical stratifications commonly encountered in the field are considered: (1) sand-uniform clay, (2) sand-nonuniform clay and (3) uniform soft clay-sand-uniform soft clay-uniform stiff clay. Further, a field case encountered in the South China Sea was provided and analyzed. The analyses are carried out using a large deformation finite-element (LDFE) approach of the Coupled Eulerian–Lagrangian (CEL) in ABAQUS/Explicit. An extended Tresca model with incorporation of strain softening through two additional parameters of δrem and ξ95 following Einav and Randolph [1] is used for the clay, whereas the Mohr–Coulomb model is adopted for the sand. In particular, a simplified method, in which no additional parameters are required as input data, is presented to predict the punch-through resistance profile of a spudcan foundation on sediments with interbedded medium-loose sand layer. By comparison with the previously published LDFE results, recent centrifuge tests data as well as measures from one field case in the South China Sea, the numerical analyses conducted in this study are verified and discussed, and better performance of the simplified method is shown for prediction of the penetration resistance profile of a spudcan foundation on sediments with interbedded medium-loose sand layer.