A novel plastic failure model of prestressed anchor cables for upper bound stability analyses of rotational reinforced slopes

In the existing upper bound limit analyses (UBLA) of rotational slopes reinforced with prestressed anchor cables, the mobilized axial forces of all cables are assumed to be equal to the ultimate pullout force. However, such an assumption overestimates the mechanical contribution of prestressed anchor cables, resulting in excessively high safety factors. In this technical note, we aim to tackle this issue by proposing a pseudo-plastic design concept, in which soil masses and prestressed cables are treated as plastic and elastic-plastic, respectively, when slopes collapse. A pseudo-plastic failure model of prestressed anchor cables is proposed, where the variation of tension forces and movement of anchor heads are accounted for. Several interesting conclusions are drawn as follows: (1) Contrary to the conventional plastic failure mode of cables, upper bound solutions obtained by the proposed model are much closer to the exact solutions. (2) Variation of factors of safety (FSs) against the accumulated rotational displacement can be explained by the force-displacement curve obtained in the pullout test of prestressed anchor cables. (3) The sliding slope reinforced with cables may turn out to be stable after a slight rotational movement, which can be utilized in the economical design.