The criteria to evaluate the efficiency of a rock-fall protection barrier based exclusively on the level of kinetic energy that may be absorbed omits the shape of the material impacting against the barrier. As the tensions in the anchorage cables are proportional to maximum deformation of the network, the efforts depend on the energy level and time over which the phenomenon acts. As with energy, if the impact times are greater, the tensions the anchorage cables bear are lower.
Thus, a Flexible Barrier that bears the impact of a rock with a specific maximum kinetic energy is able to resist the thrust and load of a Debris Flow with the same maximum energy with greater safety.
This behaviour has been calculated based on the experimental data gathered in the life size Crash Test.