Large deformation numerical analysis of rock permeability influence on anchor performance for offshore renewable applications

The rapid expansion of Offshore Renewable Energy (ORE) is leading to the development of novel rock anchoring systems which require a reliable and efficient design method to operate under strong current and tidal action. Hydromechanical (HM) coupled processes, ultimately function of the loading rate and permeability of the rock are crucial for geotechnical design. As the experimental investigation of rock-structure HM interaction is challenging, numerical modelling is often the only alternative to advance the reliability of current empirical design methods. The Geotechnical Particle Finite Element Method (GPFEM) is herein proposed to numerically assess the Rock Anchor (RA) response under axial loading in variable drainage conditions. A Structured Modified Cam Clay (S-MCC) constitutive model is adopted to represent the mechanical behaviour of a sandstone. By using a large strain non-local formulation, mesh dependency issues related to inevitable localisation processes are taken care of. Thanks to a fully HM coupled formulation the effect rock permeability on the evolution of excess pore water pressures and the mechanical response of a RA during axial pull-out is examined. The result show that these coupled HM effects play a substantial role on pull-out capacity of RA.