Design of rock fall protection structures requires information about the rock fall volume distribution. When this information is not available, rock fall volumes can be estimated based on structural information about the rock fall sources. This paper examines a rock fall source where known measurable rock falls occur. As is common, the source was inaccessible for bench scale mapping and the mapping was carried out using remote photogrammetric techniques. A discrete fracture network of the source was developed based on the remote mapping. Volume calculations followed three approaches, 1) direct measurement of loose blocks, 2) simple estimates of block dimensions, and 3) modeling of a 3-dimensional volume of rock based on the discrete fracture network. The calculations were compared against fallen rock blocks surveyed on site. The volume calculations based on the discrete fracture network were in agreement with those surveyed on site.
Design of rock fall protection structures requires information about the trajectory of the falling rock blocks and their volume [1,2,3,4]. Rock fall spatial distribution and heights are direct input for locating and dimensioning these structures, and falling block velocities and volumes (therefore their masses) are used to calculate the impact energies to be supported. Rock fall velocities are typically calculated using trajectory models calibrated against previous rock fall occurrences [5,6,7,8]. Rock fall volumes can be calculated from previous events if records are available, or from estimations of block sizes at the rock fall source [9,10,11]. The frequency distributions of rock fall velocities and volumes are combined to calculate the distribution of impact energies at any given location, which forms the basis for a reliability-based design of the protection structure.