| The capability of evaluating and managing rockfall related risks is largely
based on numerical modelling. Nevertheless, the reliability and accuracy of
rockfall models is greatly affected by the strong uncertainty and spatial
variability which characterise all the relevant parameters. In particular,
3D effects related to the variability of slope geometry and micro-topography
play a major role in controlling the dynamics of falling blocks. The most
important 3D effect is the "lateral dispersion" of rockfall trajectories,
largely affecting the way we model rockfall dynamics, design countermeasures
and assess rockfall hazard. Nevertheless, the dependence of lateral
dispersion on different controlling factors has been hardly ever
systematically evaluated.
In this paper, the influence of different controlling factors on the
dispersion of rockfall trajectories has been systematically evaluated by
performing 3D parametric modelling. Numerical simulations have been
performed through a new software code able to use both a lumped mass and an
hybrid (kinematic-dynamic) approach. Parametric modelling has been performed
at different spatial resolutions using sets of biplanar simplified slopes
characterised by different mean inclination and roughness. Model results
outlined a complex dependence of lateral dispersion phenomena on slope mean
gradient (macro-topography), slope roughness (micro-topography) and the
spatial resolution of the model (model-dependent topography). Furthermore,
the sensitivity of model results in terms of kinematic variables of motion
(i.e. velocity and height to the ground) to the factors controlling lateral
dispersion has been evaluated, resulting in practical constraints on
countermeasure design and hazard assessment. |