Three-dimensional numerical modelling of Swift Anchor for offshore renewable energy applications

Rock anchors are essential for the deployment of offshore renewable energy (ORE) systems in rocky seabed conditions. Conventional rock anchors that rely on cement-based grouting can be costly and environmentally challenging, particularly in deepwater applications. Emerging groutless self-drilling anchor technologies, such as the Swift Anchor (SA), present a promising alternative by minimising seabed disturbance and installation risks. Tensile resistance of the SA is from the mechanical interlock between the finger at the end of the anchor and the surrounding rock mass, where a pretension can be applied on the anchor head to enhance the anchor loading response. This paper develops a FLAC3D model to simulate the performance of rock anchors under combined vertical and horizontal (V-H) loading. The rock is modelled using a Hoek-Brown constitutive model, while the anchor is modelled as an elastic material. A simplified method is proposed to explicitly replicate the pretension procedure. The stiffness of load – displacement response is maximised at a loading direction of 45°, decreasing as the direction deviates from this angle. Yield limit and ultimate capacity are relatively insensitive to loading direction, suggesting the potential for a standardised SA design across a range of loading directions under the investigated ground conditions.