A low-cost terrestrial photogrammetric system for rockfall monitoring and hazard assessment in open-pit mines

Rockfalls are hazardous phenomena that can seriously affect surface mining operations and the safety of the working personnel. Monitoring and geostructural characterization are used to follow the wall activity, assess the rockfall hazard, design appropriate mitigation measures and improve risk management. For this purposes, the estimation of the size of the events and the rockfall frequency, or return period of events, is required. This paper presents a new low-cost autonomous terrestrial stereo- pair photogrammetric monitoring system developed to observe unstable volumes falling from the rock face. The system allows collecting synchronized images at different epochs and producing digital surface models. The methodology includes the automatic comparison of 3D models obtained at various epochs to track and measure rock volume detachments and surface movements. Preliminary results obtained with the proposed system by the monitoring of a sub-vertical highwall in an Australian open-pit mine over a seen week period are presented.