Investigation On The Punch-through Failure Of A Jack-Up Spudcan And Response Measures

Spudcan installation in sand overlying clay is subjected to potential punch-through hazard.Punch-through failure occurs when the applied load exceeds the maximum bearing resistance of the upper sand layer causing the spudcan to plunge into the underlying clay.Therefore,it is particularly important to predict the peak penetration resistance during the penetration process.The traditional recommended method is too conservative for the prediction of peak penetration resistance,and the newly developed prediction method still has a lot of room to improve the accuracy when calculating the underlying stiff clay.This paper based on the analysis of the punch-through failure mechanism of spudcan,the impact of the new "sand-clay" interface brought by the "soil plug" effect on the peak penetration resistance is considered.Based on visualization experiments and finite-element,consider revising the “sand-clay” interface shear strength by assuming the new interface for ideal arc and equivalent with a certain thickness of the underlying clay.The results show that the new prediction method is aimed at the underlying soft and stiff clay.The analyses are carried out using a large deformation finite-element(LDFE)approach of the Coupled Eulerian-Lagrangian(CEL)in ABAQUS/Explicit,the model consider the soil strength changes caused by the progressive failure of sand and clay strain softening,and pass the verification of the geotechnical centrifuges.A risk analysis process was established for the risk of punch-through,based on the study of existing measures,using ABAQUS investigates the potential for using skirted foundations of different lengths as an alternative to spudcan in an attempt to mitigate punch-through failure,skirted foundations is significantly effective in reducing peak penetration resistance through the comparison with the experiment.The peak resistance decreased with the increase of the length of the skirt,but it will begin to recover when the skirt length surpass sand layer thickness.Through the study also identified the most economical skirt length of choice.The reliability of the new prediction method is verified by two engineering field examples,and the results show that the new method of peak penetration resistance improves the upper limit of preload,and the finite element model established in this paper is of reference significance forthe study of spudcan in the complex seabed environment,especially in the sand overlying stiff clay layers.