Centrifuge modelling of combined anchors for slope stability

The use of combined anchoring systems for slope stability enhancement is becoming more frequent. In combined anchoring systems, active anchors (e.g. prestressed tiebacks) and passive anchors (e.g. soil nails) are used simultaneously to stabilise a slope. Although stability analysis of slopes with either active or passive anchors used separately is routine in engineering practice, experience with slopes in which these two types of anchoring systems are used in combination is considerably more limited. For example, there are questions concerning the load sharing between active and passive anchors. In this study, centrifuge tests are designed to investigate the contribution of passive anchors to the overall stability of a slope by monitoring the deformation and stress distributions in anchored slope models. Centrifuge model tests are carried out on six model slopes at the same acceleration of 100 g with different types of reinforcement: active anchors for four models and a combined anchoring system for two models. The experimental results show that the passive anchors in the combined anchoring system make an important contribution to the overall stability of the slopes. The tests are then used to verify a slope stability program that can consider both types of anchors acting together.