Numerical study of the lateral response of offshore Rock Anchors

The widespread use of Rock Anchor (RA) systems supported by the increasing demand of offshore energy requires the development of a design method that should be simple to use, efficient and most importantly reliable. In the past decade the development of such analytical tools has proven to be successful if based upon both experimental and advanced numerical analyses. Herein the Geotechnical Particle Finite Element Method (GPFEM) has been employed to assess the response of RA under lateral loading. A non-local Structured Modified Cam Clay (S-MCC) model is used to represent the mechanical behaviour of Berea sandstone. First, by means of large strain 2D plane strain simulations for horizontal sections of the anchor, the p-y response of the RA at various depths is derived numerically. The p-y curves are then used to obtain a rock anchor head horizontal displacement curve, by assuming a Bernoulli beam as representative for the RA. The newly developed p-y approach is then compared to full 3D rock-anchor interaction GPFEM simulations, to the available p-y curves, and analytical approaches found in the literature. The results show that for the type of rock investigated, the 2D plane strain simplification used to numerically retrieve p-y curves for RA is promising and sensibly efficient.