Abstract
Protection barriers against the fall of boulders and rocks are structures with non-linear mechanical behaviour that make the study particularly complex. In this study, the understanding of an experimentally observed variability was investigated numerically using a non-linear spring-mass equivalence. First, key figures of the experiments on which this study is based are detailed. Then, the numerical model for the dynamic simulation of the barrier deformation under impact is presented. Finally, the variability due to block-related parameters and then net-related parameters are explored and evidence the role of the cables’ geometric stiffness in the global response of the fence.
Highlights
The risk due to falling rocks and boulders is all the greater because it is difficult to predict it as well as to anticipate the trajectory or energy of the block [1]
It was observed that the resulting data differed significantly for the two MEL tests: there was a 13 percent difference between the two maximum displacements reached by the block, as well as a 31 percent difference in the total brake elongation
Considering that the brake threshold was constant and equal to 25 kN, this difference in the brake elongation can be interpreted in terms of energy dissipated by the brakes. Following this reasoning for MEL 2, this equivalent energy was higher than the impacting energy, which is not possible and indicates that the average threshold values must have been lower than 25 kN in this case
Summary
The risk due to falling rocks and boulders is all the greater because it is difficult to predict it as well as to anticipate the trajectory or energy of the block [1]. Passive protections must be designed to be able to stop the fall of blocks alongside more or less large areas of instability. These protections often take the form of nets supported by edge cables and posts attached to the cliff [2]. Mechanical understanding of these rockfall protections is difficult: non-linear and dynamic behaviours, in a context of large displacements and irreversible mechanisms to dissipate energy, make the study of these barriers all the more complex. Experimental tests for a better understanding at the net scale were conducted by Trad [9] and Bertrand et al [10]
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