Discontinuities are planes of mechanical weakness formed by physical interruptions in the rock mass. They are almost ubiquitous features of rock faces and include faults, bedding planes, joints, and schistosity planes. Intersections between discontinuities divide a body of rock into fragments, known as stones, blocks, or masses,according to their size, which can detach from the larger body of rock with consequences that depend on the rock fall's location and energy. Because 32% of earthwork-related incidents in the last ten years have been due to rock falls, rock face stability is a major issue in railway risk management (Pollet, 2012).