Sandy Seabed Stabilization against Wave-Included Residual Liquefaction around Marine Hydrokinetic Energy Structures using Geotextile Sand Containers

Abstract Protecting marine hydrokinetic (MHK) structures against wave-driven residual pore-pressure buildup and liquefaction is essential for reliable performance of bottom-fixed ocean renewable energy technologies. Although geotextile sand containers (GSCs) are widely used for scour protection, prior research has largely focused on the hydraulic/mechanical stability of the GSC units, with limited attention to their geotechnical role in mitigating residual liquefaction beneath MHK devices. This study provides one of the first quantitative assessments of GSC protection for mitigating wave-driven seabed instabilities beneath bottom-mounted MHK devices, and quantifies how the protection layer alters liquefaction susceptibility through cyclic stress ratio (CSR) attenuation and static shear stress ratio (SSR) redistribution. Unlike most residual liquefaction assessments that assume zero SSR, SSR effects are incorporated within a computationally efficient finite-element (FE) framework. The approach avoids the high cost of advanced cyclic plasticity WSSI models that require cycle-by-cycle hysteretic simulations. Building on the FE framework developed earlier by Rafiei (2025), SSR sensitivity is introduced via a source-term formulation within a modified Biot consolidation framework, while FE simulations provide the stress field required to compute CSR and SSR around the protected foundation. Unprotected and protected configurations are analyzed under representative storm-wave loading. Results indicate that residual liquefaction can develop beneath the unprotected foundation, whereas GSC protection can substantially suppress liquefaction by reducing CSR magnitude and modifying SSR distribution. The effects of protection layout, soil properties, and wave conditions on mitigation trends and practical design implications are discussed.