Suction Pile Allowable Suction Pressure Envelopes Based on Soil Failure and Structural Buckling

This study develops the allowable suction pressure envelopes using applicable industrial codes for different suction pile sizes at various penetration depths. In addition to the industrial codes, 3D nonlinear finite element analysis (FEA) utilizing plate buckling techniques is carried out for comparisons. Traditionally, the suction pile design has considered very comprehensive soil failure mechanisms in general practice. However, the structural plate buckling criteria for suction pile with large D/t ratios are not well defined to reflect the current industrial codes and standards. This paper performs extensive study to investigate the buckling strength of suction piles with various D/t ratios using different industrial codes and standards. This study also proposes the 3D nonlinear FEA including the geometric and material nonlinearity and using the plate buckling technique in order to predict the buckling strength for piles with various D/t ratios. The above approaches can provide thorough comparisons among different code requirements and FEA results. After suction pile's self-penetration, the initial suction pressure required to mobilize the force penetration can be critical for pile shell buckling, especially for the large D/t and long pile. This required suction pressure due to moderate soil setup and static friction is briefly discussed in this paper. Based on this study, different codes and standards suggest different buckling strengths to the same pile. In general, for piles with D/t ratio less than 120 and with small L/D ratio, the suction pressure to fail the pile structure is much higher than that for the soil plug failure in regular clay soil; nevertheless, this may not be applicable for piles with D/t ratio greater than 120 and with large L/D ratio. The industrial codes and standards using thin wall theories shall be adopted to design suction piles w in order to take into account various structural buckling modes. For the 3D nonlinear FEA, the post buckling analyses predict the suction pile buckling pressures and show the reduction in pressure after buckling rather than traditionally selected buckling pressure at an arbitrary displacement regardless pile geometries. The proposed approaches to generate the allowable suction pressure envelopes can lead to an economical suction pile design and provide the installation contractor with a visualize tool to ensure a safe and successful suction pile installation.