Suction Pile Seabed Landing and Vents Calculation

Abstract A computer program has been developed to simulate the landing of suction piles on the seabed. The procedure is based on the dynamic analysis procedure outlined in DNVGL-RP-N103 (DNVGL 2017) and calculates the pile motion as it penetrates the soil using a time integration scheme to simulate the dynamic seabed landing. The analysis method considers all significant forces acting on the pile with their time-dependent values, including gravity, buoyancy, crane wire tension, hydrodynamic pressure within the pile, and soil resistance. The program can be used for a given pile geometry to determine the maximum allowable lowering velocity that does not lead to foundation failure. Or for a given lowering velocity, determine the minimum allowable vent area in the pile. The DNVGL procedure is numerically challenging to implement because iterating on the main unknown variable (the incremental soil displacement) using the last known state parameters will not necessarily lead to convergence towards the ‘correct’ solution. The use of a line search algorithm is proposed to overcome this issue. The results of a sensitivity study are briefly presented to investigate how the main parameters influencing the results. The dynamic analysis method is also compared to the traditional ‘simplified method’ of DNVGL-RP-N103 Section 6.2.6 which considers only static forces acting on the pile and neglects the beneficial dynamic effects of damping. The advantages of using the dynamic method over the simplified method is discussed.