This paper presents an approach to rockfall hazard assessment for open-pit mining faces in a quartzite mine. The proposal is based on geomechanical characterization of rock masses, indications of event activity, external influences, event intensity, slope geometry and the characteristics of the catchment area. In this method, the hazard is given by a matrix of probability versus intensity. Seven open-pit mining faces were analyzed in a quartzite mine, located in São Thomé das Letras, Minas Gerais State (Brazil). Most of the slopes were considered to be hazardous, due to the structural characteristics of the discontinuities, slope height and indications of activity. The reduction of the slope height with the construction of benches and the cleaning of the mining faces are possible mitigation measures to prevent rock blocks from falling. Benches with about 7 to 8 m of height and safe berm width about 5 m were proposed.
Nowadays, new systems for the assessment of susceptibility, vulnerability, hazard and risk have been increasingly proposed because they are rapid easy-to-use tools for accident prevention, especially in geotechnical problems, like slope stability.
The quartzite rock mass of São Thomé das Letras region (Minas Gerais, Brazil) is characterized by being foliated and this is a factor that facilitates its extraction and processing for use as an ornamental rock. On the other hand, the foliation, connected to other discontinuities and cracks generated by blasting, can lead to rockfall problems.