Recent advancements in marine geotechnical engineering are addressing the challenges posed by offshore structures as demands for marine energy escalate. One significant concern is the pullout resistance of plate anchors, fundamental components of anchoring foundations used extensively across drilling platforms and wind farms. A new study has implemented finite element analysis to investigate the pullout resistance and progressive failure mechanisms of strip anchors embedded within strain-softening marine soils.
This research utilizes a Cosserat continuum regularization mechanism coupled with the Mohr-Coulomb matched Drucker-Prager (MC-matched DP) constitutive model. By employing the User-Defined Element (UEL) feature within the finite element software ABAQUS, the authors aimed to address traditional numerical convergence issues and mesh dependency often encountered when analyzing softening soils.
The study confirmed the reliability of the MC-matched DP model by validating its output against existing literature, ensuring its robustness for calculating pullout resistance under strain-softening conditions. According to the authors, “the Cosserat continuum model effectively resolves common issues such as numerical convergence difficulties and mesh dependency,” indicating significant improvements over classical models.
Parametric analyses shed light on the interplay between anchor plate inclination, burial depth, and the degree of strain softening, leading to new insights on their combined effects on ultimate pullout resistance. The ultimate pullout resistance coefficient (Nc), influenced strongly by embedment ratio (H/B) and softening modulus (hp), was analyzed under different conditions. The findings indicated, “in shallow burial conditions (H/B < 4), the pull-out resistance of the anchor plate is relatively low and increases gradually with increasing H/B,” providing practical guidelines for engineers designing anchoring systems.
One of the key findings revealed how the softening modulus directly impacts performance. For various inclination angles, Nc showed consistent trends, decline as hp increased. This exploration opens avenues for designing more resilient anchoring systems by informing how to effectively mitigate the risks associated with soil softening.
The study's methodology not only offers concrete improvements to finite element modeling among softening soils but also provides comparable resistance estimates through derived expressions for Nc under varying conditions. These efforts lend tangible support to geotechnical engineers striving to optimize offshore constructions and manage the nuances presented by marine soil behaviors. Notably, through parametric studies, the research indicates clear pathways for practical applications: “an expression for Nc was derived, which simultaneously accounts for the effects of plate anchor inclination, burial depth, and strain softening,” thereby equipping practitioners with analytical tools to evaluate and improve anchor resilience.
While the study achieves significant initial insights, the authors note inherent limitations surrounding the modeling assumptions employed, particularly concerning post-failure behavior under large plastic deformations. They state, “the Cosserat finite element model requires enhancement by incorporating a nonlinear strain-softening mechanism,” highlighting the need for future research to refine predictive capabilities of such modeling approaches.