Influence of Soil Backflow and Punch-Through Phenomenon on Spudcan Penetration in Two-Layer Soil Formations

Abstract

Abstract This study seeks to investigate the influence of backflow soil and punch-through phenomena on the bearing resistance profile of the Spudcan penetration. These factors have the potential to induce abrupt failures in jack-up barges during both installation and operation phases. A recently developed finite element technique called the Press Replace Technique (PRT) is being used to study this problem. The PRT has proven to be one of the most efficient techniques for assessing the stability of a Jack-up barge under the design vertical loads during installation and operation. This method ensures a satisfactory bearing capacity, an adequate embedded depth of a Spudcan foundation, and, consequently, a stable installation of a Jack-up barge. The study shows the main criteria and the basic assumptions to be considered in the finite element analysis using the PRT, including the modelling technique of the backflow phenomenon in case the surface layer is a clay soil. The study primarily focuses on double-layer soil conditions, particularly, the condition of stiff clay over soft clay and the condition of stiff clay over loose sand conditions, where Punch-Through of a Spudcan is more likely to occur. A practical case study analyzes a scenario where the Spudcan penetrates through a thick surface layer of soft clay over a layer of sand. The findings underscore the necessity of incorporating the backflow phenomenon in the numerical analysis, particularly in relation to the occurrence of punch-through. Furthermore, when considering double-layer with a surface clay layer, the results indicate that the bearing resistance of the surface layer is predominantly influenced by the type and thickness of the soil layer underneath.