An incrementally updated nonlocal RITSS framework for strain-softening clay with application to cyclic caisson penetration

Mesh-dependent localisation complicates large-deformation analysis of strain-softening clay under cyclic loading and repeated remeshing. This study develops an incrementally updated nonlocal framework for the remeshing and interpolation technique with small strain (RITSS). After each converged equilibrium increment, the plastic-strain measure governing strength degradation is spatially averaged, thereby reducing the lag associated with updates performed only at remeshing stages. During remeshing, the nonlocal history is transferred, whereas the neighbourhood and weights are reconstructed and reused within each stage. The method is implemented in Abaqus/Standard through field-dependent strength properties, allowing the built-in material models to be used without developing a custom stress-integration routine. Plane-strain and axisymmetric localisation tests verify the regularisation capability, while a centrifuge caisson penetration benchmark and displacement-controlled monotonic and cyclic caisson analyses demonstrate the framework in a moving-boundary problem with contact and repeated remeshing. For the examined mesh sizes of 0.10, 0.15 and 0.20 m, the spread in final penetration resistance, defined as the range divided by the mean, decreases from approximately 18.7% to 4.1% under monotonic penetration and from 25.9% to 5.8% under cyclic penetration. These results demonstrate improved mesh robustness within the investigated mesh range and under the adopted rough-interface condition.