Load-controlled element-by-element method incorporating skew-boundary condition for soil-structure interactions: application to punch-through analysis of the 3D jack-up rig

The jack-up structure is commonly used as the oil and gas platforms or the drilling rig in offshore applications with its major failure mode being punch-through failures. Numerical investigation of this punch-through behavior has rarely been performed through a full-scale 3D analysis considering both the complete jack-up structure and the underlying soils due to the high computational cost to solve such a large system with millions of degrees of freedom. This paper develops a new algorithm by combining the element-by-element preconditioned conjugate gradient method with (a) the interface model for the skew boundary condition, (b) a load-controlled algorithm based on the generalized stiffness parameter, and (c) the viscoplastic Mohr-Coulomb model for soils. Model verification is performed by comparing the simulated bearing capacity of a single spudcan with those obtained from different design methods (e.g., the ones by the Society of Naval Architects and Marine Engineers (SNAME), International Organization for Standardization (ISO)) and numerical solutions. Then, the punch-through failure of a 3D jack-up rig resting on a layered soil is investigated with the full-scale 3D simulation. The bearing capacity of each spudcan is discussed and soil behaviors around spudscans during punch-through failures are investigated.