Ultimate pullout capacity of strip plate anchors in shallow rock masses

The increasing demand for offshore engineering solutions and the growing complexity of modern infrastructure necessitate reliable rock anchor systems with sufficient pullout resistance. However, research on rock anchors incorporating nonlinear strength criteria remains limited. This study introduces a semi-analytical approach based on kinematic limit analysis, integrating the generalized Hoek–Brown failure criterion to assess the ultimate pullout capacity of shallow rock anchors. A segment-based failure mechanism is developed to model the curvature of the failure surface using piecewise linear segments, balancing accuracy and computational efficiency. A systematic evaluation of confining stress ranges reveals that the stress conditions of shallow anchors are primarily governed by overburden stress rather than rock mass strength parameters, leading to a proposed general stress range of 0 ≤ σ₃ ≤ 0.55γH. When applied to variational analysis—an approach requiring an approximate shear strength envelope—the proposed stress range results in near-exact agreement with the segment-based approach. Further parametric studies highlight the significant influence of rock mass properties and anchor characteristics on pullout capacity and failure mechanisms. The proposed approach fully preserves the generalized Hoek–Brown criterion, offering a more rigorous and flexible method for evaluating shallow rock anchor stability and advancing analytical techniques in offshore engineering.