Advanced Continuum Modeling of Pile Response to Jack-up Spudcan Penetration

Jack-up rigs are mobile offshore structures that are founded on the seabed with the aid of spudcans or matted foundations. These foundations are connected to trussed or tubular legs supporting the rig hull and the legs can be jacked vertically during installation. To ensure stability of the rigs and to reduce the risks of instability arising from causes such as scouring, leg punch-through, etc., adequate spudcan penetration into the soil is required. Deep penetration of the spudcan causes large soil deformation. If the spudcan is close to any existing structures, the penetration may cause deformation to the structure foundation, such as pile foundation of existing jacketed platforms. As a result, a need exists to assess this problem. Numerical modeling of the process of spudcan penetration adjacent to an existing pile foundation is a challenging problem due to the complexity of interaction between the spudcan, soil and pile. In addition, soil has a very complex constitutive behavior which is strongly dependent on soil stratigraphy, soil type (sandy vs. clayey soils) within each layer and loading conditions (drained vs. undrained). This paper describes an advanced 3D continuum finite element analysis methodology using Explicit Coupled Eulerian Lagrangian (CEL) technique to simulate the spudcan penetration into soils and evaluate the effects of spudcan penetration on adjacent pile foundation. Soil and pile responses to the spudcan penetration are presented in this paper. As the state-of-practice to evaluate the pile response is an un-coupled approach by solving the soil and pile response separately, this paper also compares the coupled/un-coupled analyses to evaluate pile response to large soil deformation.