Study on the Evolution Process of Toppling Rockfall and Their Monitoring and Warning Index

A toppling rockfall is one of the most common failures on slopes, particularly rock slopes, with a set of discontinuities dipping steeply into the slope face and striking approximately parallel to it. Toppling failures are frequently observed along man-made highway infrastructures, open-pit mines, and underground mining slopes, resulting in massive damages to facilities and risks to human lives. However, the current experimental methods pose a challenge to predicting and preventing the rockfall hazards. This study aimed to identify and describe the general toppling evolution of a single-column block and understand its deformation and failure behaviors through on-site and laboratory model experiments. Toppling rockfall was divided into four evolutionary processes: initial deformation, accumulation of cracks, rapid spread of fractures, and failure of the locking section. The displacement, dip angle, and acoustic emission each have a different evolutionary process indicative of toppling collapse. Displacement and dip angle can reveal the suddenness of the collapse (sudden change before failure), while the sound emission index can reveal the expansion and penetration of internal fractures in advance, compared to displacement and dip angle, which provides advanced warning of collapse.