Centrifuge modelling of the influence of slope height on the seismic performance of rooted slopes

This paper presents an investigation into the influence of slope height on the role of vegetation to improve seismic slope stability. Dynamic centrifuge modelling was used to test six slope models with identical soil properties and model slope geometry within different centrifugal acceleration fields (10-g and 30-g, respectively) representing 1:10 and 1:30 scale slopes, i.e. slopes of different height at prototype scale. A 3-D root cluster analogue representing a tap-root system, with root area ratio (RAR), root distribution and root length representative of a 1:10 and 1:30 scale tree root cluster (of rooting depth 1.5 m at prototype scale) was modelled using 3-D printing techniques. A sequence of earthquake ground motions was applied to each model. The influences of filtering out low frequency components of the earthquake motion, such as was necessitated at the lowest scaling factor due to the practical limitations of the earthquake simulator, on dynamic amplification of motions within the slopes and the seismically induced slip, were firstly revealed. Subsequently, the effects of slope height on acceleration and deformation response of vegetated slopes were illustrated. It was found that the beneficial effects of roots on improving the seismic performance varied with the height of the slope. As an individual engineering technique for slope stabilisation, root reinforcement will not be such an effective solution for taller slopes and complementary hard engineering methods (e.g. piles, retaining walls) will be necessary. But for slopes of smaller heights (e.g. low height embankments along transport infrastructure), vegetation appears to represent a highly effective method of reducing seismic slip.