Reinforced behaviors of anchored slopes with weak layer: insights into effect of weak layer and anchorage angle

Abstract Purpose The investigation on deformation trajectories and damage morphology of bedding rock slopes with weak layers is a prominent concern within the slope engineering field. Multi-field information is instrumental in elucidating the evolutionary process of deformation and potential damage modes of these slopes. Method Based on field investigations of the slope in the vicinity of the Baihetan Hydropower Station, this study conducted a series of physical modelling tests encompassing 3 weak layer percentage and 3 anchorage angle combinations. The aim of the 5 sets of tests was to explore the deformation and failure mechanisms in landslide using a multi-field monitoring system combined with DIC technology. Result The observation during the deformation failure stages revealed how variations in the weak layer percentages and the anchorage angles influence rock mass deformation and failure characteristics. Simultaneously, a quantitative relationship between the weak layer percentages and anchorage effectiveness was established for the first time through physical modelling tests. Conclusion The findings highlight that weak layers can directly influence the load transfer patterns of anchors while simultaneously inducing significant strain concentration phenomena. The anchor strain of rock slopes with 34% of weak layers is increased by 79.4%. An anchorage angle of 25°, accompanied by a reduction in anchor strain of 48.6%. Additionally, the anchorage angle significantly affects the expansion location of landslide cracks. The number of landslide cracks is relatively low when the anchorage angle is 25°, and these cracks primarily occur along the rear edge of the landslide. Consequently, an anchorage angle of 25° is identified as optimal angle among 3 anchorage angles for mitigating rock landslides. Based on multi-field coupling monitoring data, the evolution stage of slope is segmented into four stages for the first time, namely, micro-crack stage, macro-crack stage, near slip stage and slip failure stage. Investigating the force characteristics and anchor load transfer mechanism of anchored rock landslides with weak layers helps to provide engineers with recommendations for designing schemes to support these landslides.