The Coupled Eulerian-Lagrangian finite element technique (CEL technique) is an effective numerical method to analyze effects of spudcan penetration on adjacent piles. The stratum with large deformation is modeled as the Eulerian domain and the other strata are modeled as the Lagrangian domain in the CEL finite element model. The responses of adjacent piles depend on the Eulerian domain size. The paper researches the effects of the Eulerian domain size on responses of adjacent piles in the clay based on centrifuge model test results. For fixed-headed piles, results show that the proper depth of the Eulerian domain is 1.0 to 1.5 times the diameter of the spudcan below the seabed if the spudcan penetration depth is less than 0.75 times spudcan diameter, and the depth of the Eulerian domain is taken as about 1.5 times spudcan diameter below the seabed if the penetration depth is larger than 0.75 times spudcan diameter. For free-head piles, results show that the proper depth of the Eulerian domain is 1.0 to 1.5 times spudcan diameter below the seabed if the penetration depth is less than 0.6 times the spudcan diameter, and the depth of the Eulerian domain is taken as 2.0 to 2.5 times spudcan diameter below the seabed if the penetration depth is larger than 0.6 times the spudcan diameter.
The spudcan with large diameter will be penetrated into strata to supply the sufficient bearing capacity for operations when a mobile jack-up is conducting drilling and fixing works in close proximity to a permanent Jacket platform in offshore oil and gas development, which inevitably brings great risk to pile foundations of the adjacent platform. For example, the maximum diameter of the spudcan of HYSY941 used by China Oilfield Services Ltd is 18m and the minimum operation distance between the spudcan and the pile foundation of the platform is only 0.4 times the diameter of the spudcan. Moreover, the penetration depth exceeds 10m in fields with soft strata, which will result in a large amount of squeezed soil and induce extreme bending moment and shear force to adjacent piles. One of challenging problems is to assess the effects of spudcan penetration on adjacent pile foundations for the ocean engineering. However, studies on effects of spudcan penetration on adjacent piles are relatively scarce to date.
