Suction caissons are used to fix submarine systems of production into the seafloor for exploding hydrocarbons. The foundations of submarine systems are subjected to combined or multiaxial loading, which consists in applying combinations of horizontal and vertical loading (H,V) with driving moments (M). The main objective of this research work was to estimate numerically the combined capacity by means of failure envelopes of a suction pile installed in normally consolidated soil and subjected to combined loading applied at the head. The failure envelope represents the boundary of the combination of loading that the pile-soil can withstand. Finite element program ANSYS® 14.5 was used to model the caisson-soil system and evaluate the capacity of the caissons subjected to 17 combinations of HM failure loading and 22 linked values of VM maximum loading. Each numerical result permit to conform failure surfaces, which for the HM capacity exhibit rotated elliptical shapes with clear symmetry, while failure envelopes of the MV plane exhibit thong-shape failure and are clearly non-symmetrical. In this research, the pure compressional capacity was 72% higher than the pure extensional capacity. The mechanisms of failure of the caissons loaded at the head meet very well with the modes reported in the oil industry. Caissons subjected to horizontal loading in positive convention (applied from left to right direction) and clockwise moment exhibited "external-scoop" mechanisms, while caisson under positive lateral loading and counter-clockwise moments might experience translational or rotational failure mechanisms. Finally, this research work permit to quantify the impact of the variation of the mechanical properties of the soil on the caisson capacity as well as the type and size of the failure modes of the foundation.
A risk and reliability based calibration of partial safety factors for the ultimate limit state of suction caissons subjected to inclined tension loads from floating production systems is presented. The formulation is for the case of normally consolidated clay deposits with undrained loading conditions.
The load capacity analysis is carried out using the plastic limit model proposed by Aubeny et al. [1–3]. A procedure to calibrate the plastic limit model based on finite element numerical results is described. Line tensions from two mooring systems of an FPSO designed for two sites in deep water at the Bay of Campeche, Gulf of Mexico, are used.
A procedure to characterize probabilistically the load capacity of the caisson at mudline is presented. The physical lower limit of the load capacity and soil-chain interaction are taking into account. The mean and dynamic tensions of mooring lines are modeled through response surfaces in terms of uncertain metocean variables describing extreme sea-states. Reliability analyses are performed using FORM and considering both mooring line tensions and load capacity of the soil-caisson system at the mudline, rather than at the padeye. Partial safety factors for the design of caissons in connection to catenary and taut-leg mooring systems are calibrated separately. This is considered to be most appropriate taking into account their differences in terms of relative contributions of the mean and dynamic tension components, failure mechanisms controlling the loading capacity, and lower bound capacity. Calibration of safety factors is performed for a target reliability index equal to 4.2.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.