Evaluation of Ultimate Pullout Capacity of Anchor Cables Embedded in Rock Using a Unified Rupture Shape Model

Abstract

Anchor cables are now widely used to stabilize many kinds of geostructures in practice. However, the prediction of the anti-pullout performance of anchor cables still involves uncertainty for designer. This paper presents an analysis procedure for the evaluation the ultimate pullout capacity of anchor cables embedded in rock. A unified rupture shape model is proposed to describe the failure surface shape of anchor in rock mass by incorporating typical failure mode and failure surface shape. Using the limit equilibrium method, a formula of ultimate pullout capacity of a single anchor (cable) considering layout pattern, grouting pressures, rock masse quality and construction disturbance is then established with the assumption that surrounding rock follows the generalized Hoek–Brown criterion. Performance of the present method is assessed using comparison of the theoretical and well-documented filed test results. Parametric study is also carried out to clarify the influence of some key indices for rock mass on the ultimate pullout capacity of anchor cables embedded in rock. The present analyses shows that the geological strength index has great influence on ultimate pullout capacity of a single cable and ultimate pullout capacity of a single cable could be improved to a certain extent by reducing construction disturbance.