The danger of rock falls is increasing day by day due to climatic changes. This was once restricted to mountainous regions, but expanding urban areas close to rocky slopes are increasingly at risk. Conventional protective structures are often unable to withstand those risks. We have solutions for every rock fall hazard from low to exceptionally high impact energy levels.
The three basic stages of rock falls are considered:
1) The triggering stage
2) The motion stage
The interaction with a structure stage;
Along with contributions including structural characterization of cliffs, remote monitoring, stability analysis, boulder propagation, design of protection structures a risk assessment. Academic contributions are illustrated by practical examples, and completed by engineering contributions where practical purposes are thoroughly considered. The first one is linked to the experimental revolution in the measurement and monitoring means, used to quantify the displacements fields in situ in a very accurate manner (global positioning systems, photogrammetry, etc) and to characterize the kinematic discontinuities existing at various scales in all rock bodies (laser scanning, InSAR, novel geophysical methods, etc.) The second reason corresponds to the unexpected power of the new numerical methods to catch and describe quantitatively the main continuous and discrete aspects in the deformation of a rock cliff, in its failure and finally in the flow of the resulting blocks Both the first reasons have induced the current considerable enlargement of the available techniques to preserve constructions and infrastructures subjected to rock falls, by
considering not only various types of embankments or rigid structures but also flexible ones with net barriers By walking in mountainous regions everybody can in fact observe the continuous nature of the rock matrix and, on the other hand, the discrete aspects of rock blocks. By considering the first aspect as predominant, that has led us to analyze rock slope stability by the methods of limit equilibrium then generalized into the methods of limit analysis.
However rock failure is generally discontinuous and to take this aspect into account properly some numerical methods stemming from molecular dynamics are now available. One of them is particularly adapted to rock mechanics; this is the so called “discrete element method”, where (as generally in molecular dynamics) the rock blocks are considered as geometrically isolated individuals in interaction with each other. This kind of analysis allows us, in a very natural manner, to develop trajectory analysis tools, which are currently able to describe the propagation of a rock fall in a more quantitative way following the basic advances in rebound mechanics. The kinematic discontinuities in a rock slope are usually called “rock joints”, which are generally in filled by some natural geo-materials mainly coming from the aging, degradation and damage of the rock matrix.