Dynamic Interaction Between SCR and the Seabed

The interaction between a Steel Catenary Riser (SCR) and seabed soil is extremely complicated, in which the supporting force of soil to the riser is nonlinear and time dependent, and soil absorbs the energy of the motion of a SCR near its Touch Down Zone (TDZ). The magnitude of soil stiffness is crucial to the fatigue life of a SCR and the damping of soil may play an important role in reducing the motion of a SCR near its TDZ. Therefore, it is important to allow for a realistic behavior of seabed soil in simulating the interactions between SCRs and the seabed and between a floating structure and its SCRs. Recent studies on the behavior of seabed soil in interacting with risers have resulted in more realistic P-y curves of the seabed soil, where P stands for the supporting force of soil and y for the vertical penetration of the riser with respect to the seabed surface. This study extends an existing finite element numerical code for dynamic analysis of mooring lines and risers, known as CABLE3D, to allow for the low boundary condition of a SCR at the seabed to be described by a P-y curve or an approximation of the P-y curve instead of simplified linear springs. The results of the extended CABLE3D can lead to a more accurate estimate of the fatigue life of a SCR.