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The present article exposes the procedure to achieve the three-dimensional geometric model of a rock mass from a pair of photographic shots made with a current camera, use of free/open software such as Octave and other free libraries, construction of equipment and simple tools and the appropriation of important knowledge in artificial vision. It is described taking as an example the three-dimensional model of a blast cut of the rock mass of the Santa Rita Quarry, located southwest of the city of Medellín (Colombia). Finally, it is shown by a validation, based on field measurements, that the procedure described here is promising so that it can be established as a tool for the geometric characterization of discontinuities of rock mass., El presente artículo expone el procedimiento para lograr el modelo geométrico tridimensional de un macizo rocoso a partir de un par de tomas fotográficas hechas con una cámara corriente, uso de software libre/abierto como Octave y otras librerías libres, construcción de equipos y herramientas sencillos y la apropiación de conocimientos importantes en visión artificial. Se describe tomando como ejemplo el modelo tridimensional de un corte de voladura del macizo rocoso de la Cantera Santa Rita, localizada al sudoeste de la ciudad de Medellín (Colombia). Finalmente, se muestra mediante una validación, a partir de medidas de campo in situ, que el procedimiento descrito aquí es promisorio para que pueda instaurarse como una herramienta para la caracterización geométrica de discontinuidades de los macizos rocosos.

The present article exposes the procedure to achieve the three-dimensional geometric model of a rock mass from a pair of photographic shots made with a current camera, use of free/open software such as Octave and other free libraries, construction of equipment and simple tools and the appropriation of important knowledge in artificial vision. It is described taking as an example the three-dimensional model of a blast cut of the rock mass of the Santa Rita Quarry, located southwest of the city of Medellín (Colombia). Finally, it is shown by a validation, based on field measurements, that the procedure described here is promising so that it can be established as a tool for the geometric characterization of discontinuities of rock mass., El presente artículo expone el procedimiento para lograr el modelo geométrico tridimensional de un macizo rocoso a partir de un par de tomas fotográficas hechas con una cámara corriente, uso de software libre/abierto como Octave y otras librerías libres, construcción de equipos y herramientas sencillos y la apropiación de conocimientos importantes en visión artificial. Se describe tomando como ejemplo el modelo tridimensional de un corte de voladura del macizo rocoso de la Cantera Santa Rita, localizada al sudoeste de la ciudad de Medellín (Colombia). Finalmente, se muestra mediante una validación, a partir de medidas de campo in situ, que el procedimiento descrito aquí es promisorio para que pueda instaurarse como una herramienta para la caracterización geométrica de discontinuidades de los macizos rocosos.

The present article exposes the procedure to achieve the three-dimensional geometric model of a rock mass from a pair of photographic shots made with a current camera, use of free/open software such as Octave and other free libraries, construction of equipment and simple tools and the appropriation of important knowledge in artificial vision. It is described taking as an example the three-dimensional model of a blast cut of the rock mass of the Santa Rita Quarry, located southwest of the city of Medellín (Colombia). Finally, it is shown by a validation, based on field measurements, that the procedure described here is promising so that it can be established as a tool for the geometric characterization of discontinuities of rock mass., El presente artículo expone el procedimiento para lograr el modelo geométrico tridimensional de un macizo rocoso a partir de un par de tomas fotográficas hechas con una cámara corriente, uso de software libre/abierto como Octave y otras librerías libres, construcción de equipos y herramientas sencillos y la apropiación de conocimientos importantes en visión artificial. Se describe tomando como ejemplo el modelo tridimensional de un corte de voladura del macizo rocoso de la Cantera Santa Rita, localizada al sudoeste de la ciudad de Medellín (Colombia). Finalmente, se muestra mediante una validación, a partir de medidas de campo in situ, que el procedimiento descrito aquí es promisorio para que pueda instaurarse como una herramienta para la caracterización geométrica de discontinuidades de los macizos rocosos.

In this paper, two analytical procedures which are independent from the existence of empirical data are presented for the calculation of (1) the size distribution of potentially unstable rock masses that expresses the potential rockfall size distribution, including big volumes corresponding to potential rare events with low susceptibility of failure and (2) the in situ block distribution on the slope face. Two approaches are, respectively, used. The first one involves the detection of kinematically unstable surfaces on a digital elevation model (DEM) and on orthophotos and the calculation of the volumes resting on them. For the second one the in situ block volumes formed by the intersection of the existing discontinuity sets are calculated using a high-resolution DEM. The procedures are presented through an application example at the country of Andorra and in particular at the chute of Forat Negre. The results from the first procedure indicate that it is kinematically possible to have mobilized volumes of some thousands of cubic meters; however, these are considered rare events with low susceptibility of failure. The size distribution of potentially unstable rock masses for big volume events was well fitted by a power law with an exponent of -0.5. The in situ block distribution on the slope face from the second procedure, assuming three types of intersection between the joints of the existing discontinuity sets and two extreme cases of discontinuity persistence, was also found to follow a power law, but with an exponent of -1.3. The comparison with the observed in the field block volume distribution on the slope face indicates that in reality discontinuities have a very high persistence and that considering only their visible trace length overestimates volumes, which is conservative., Peer Reviewed, Postprint (author’s final draft)