Monitoring and geomechanical evaluations at an open pit marble quarry

The paper reports a geomechanical monitoring and measurements experience at an open pit quarry. The quarry site belongs to an Alpi Apuane white marble basin (Carrara marble), where intensive quarry exploitations (both open pit and underground) have been developed. The high level of mechanization and new marble cutting technology have favoured an increase in these exploitations making an experimental evaluation of the static condition, both at the exploitation workplaces and of the permanent residual rock structures, necessary. Planning of the ground control was driven by the specific geostructural and mechanical rock mass characteristics of the site in consideration of the particular geometry of the residual rock face. This control activity plays an important role on the safety and planning of further quarry deepening. The potential of rock block instabilities was estimated on the basis of a geostructural rock mass characterization and the block theory. A monitoring program of the structurally controlled deformation of the excavated rock face was set up and it allowed a displacement progression to be detected at some locations on the rock face. Hydraulic fracturing stress measurements were also carried out at different locations and depths on quarry floor of the quarry and they showed a high horizontal stress level at a shallow depth.