Subsea pipelines in Arctic environments face the risk of damage from ice gouging, where drifting ice keels scour the seabed. To ensure pipeline integrity, burial using methods like ploughs, mechanical trenchers, jetting, or hydraulic dredging is the conventional protection method. Each method has capabilities and limitations, resulting in different trench profiles and backfill characteristics. This study investigates the influence of these trenching methods and their associated trench geometries on pipeline response and seabed failure mechanisms during ice gouging events. Using advanced large deformation finite element (LDFE) analyses with a Coupled Eulerian-Lagrangian (CEL) algorithm, the complex soil behavior, including strain-rate dependency and strainsoftening effects, is modeled. The simulations explicitly incorporate the pipeline, enabling a detailed analysis of its behavior under ice gouging loads. The simulations analyze subgouge soil displacement, pipeline displacement, strains, and ovalization. The findings reveal a direct correlation between increasing trench wall angle and width and the intensification of the backfill removal mechanism. Trench geometry significantly influences the pipeline's horizontal and vertical displacement, while axial displacement and ovalization are less affected. This study emphasizes the crucial role of trenching technique selection and trench shape design in mitigating the risks of ice gouging, highlighting the value of numerical modeling in optimizing pipeline protection strategies in these challenging environments.

The progression of marine resource exploration into deepwater and ultra-deepwater regions has intensified the requirement for precise quantification of the undrained shear strength of clay. Although diverse in situ testing methodologies-including the vane shear test (VST), cone penetration test (CPT), T-bar penetration test (TPT), and ball penetration test (BPT)-are widely utilized for the assessment of clay strength, systematic discrepancies and correlations between their derived measurements remain inadequately resolved. The aim of this work is to provide a systematic comparison of strength interpretations across different in situ testing methods, with emphasis on identifying method-specific biases under varying soil behaviors. To achieve this, a unified numerical simulation framework was developed to simulate these four prevalent testing techniques, employing large-deformation finite element analysis via the Coupled Eulerian-Lagrangian (CEL) approach. The model integrates critical constitutive behaviors of marine clays, specifically strain softening and strain rate dependency, to replicate in situ shear strength evolution. Rigorous sensitivity analyses confirm the model's robustness. The results indicate that, when the stain rate and softening effects are neglected, the resistance factors from the CPT and VST remain largely insensitive to shear strength variations. However, T-bar and ball penetrometers tend to underestimate strength by up to 15% in high-strength soils due to the incomplete development of a full-flow failure mechanism. As a result, their application in high-strength soils is not recommended. With both the strain rate and softening effects considered, the interpreted strength value Sut from the CPT increases by 13.5% compared to cases excluding these effects, while other methods exhibit marginal decreases of 4-5%. The isolated analysis of strain softening reveals that, under identical softening parameters, the CPT demonstrates the least sensitivity to strain softening among the four methods examined, with the factor reduction ratio Ns/N0 ranging from 0.76 to 1.00, while the other three methods range from 0.65 to 0.88. The results indicate that the CPT is well suited for strength testing in soils exhibiting pronounced softening behavior, as it reduces the influence of strain softening on the measured results. These findings provide critical insights into method-specific biases in undrained shear strength assessments, supporting a more reliable interpretation of in situ test data for deepwater geotechnical applications.