Three dimensional finite element modeling for the spudcan penetration into clayey seabed

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2015

Öğrenci: VOLKAN EMREN

Danışman: NEJAN HUVAJ SARIHAN

Özet:

The penetration of the foundation for “jack-up rig” type offshore oil platform (spudcan) into a uniform clayey seabed is studied with three dimensional finite element modeling (Abaqus 6.14) using Coupled Eulerian Lagrangian method. Although there exists some analytical methods (InSafeJIP etc.) for the calculation of the spudcan bearing capacity, they frequently underestimate or overestimate the bearing capacity due to simplifications involved. For the spudcan geometry and soil properties used in this study, based on the 3D FEM analyses, the required penetration depth for a target bearing capacity of spudcans can be reduced by 2 to 4 m. Rate of increase of the bearing capacity with depth is larger in 3D FEM analyses as compared to InSafeJIP method, which may also result in significant savings, however this finding is limited for the spudcan geometry and soil properties used in this study. A systematic parametric study is conducted for the variables that affect the spudcan penetration resistance. These parameters were spudcan diameter (7.5 to 15 m), spudcan cone angle (90 to 150 degrees), roughness of spudcan surface (roughness coefficient of 0 to 1.0), undrained shear strength of clay (20 to 80 kPa), spudcan penetration depths (3 to 20 m), and the spacing between two adjacent spudcans (spacing/diameter ratio of 1.5 to 3.0). Based on these results, spudcan size, cone tip angle etc. can be selected, for each case, to provide required penetration resistance and/or to reduce the required penetration depth. Understanding the relations between the factors and penetration resistance based on this study, may provide a significant step in enhancing the safe and economical design and successful penetration operation of spudcans. However, it should not be forgotten that, the key is to have extensive and correct information and interpretation about the subsoil profile and material properties.