Remote sensing techniques in underground mining: Application of terrestrial LIDAR for stability analysis and optimization of excavation activities

A detailed knowledge of the structural setting of a rock mass is undoubtedly essential for proper planning of safe excavation activities. Terrestrial LiDAR technology can allow detailed remote data acquisition not only for mine rock faces but also for discontinuities. This remote data collection can be combined with traditional engineering-geological surveys in the deterministic mapping of the discontinuity sets to be used in stability analysis. In addition, tunnel excavation within a rock mass changes the pre-existing stress state, which can induce brittle deformations that may lead to instability in the excavation walls and a reduction of the quality of the extracted material. It is therefore very important to consider changes over time in stress orientation and stress magnitude in the mining area; these are influenced by both new tunnel excavations and by the presence of discontinuities, especially within a competent marble rock mass. This case study provides an example of a working approach that combines terrestrial LiDAR and traditional geological surveys for engineering-geological investigations. A three-dimensional model, which includes information about the geological structures in an underground marble mine in the Apuan Alps, is combined with information about discontinuities identified and mapped in a deterministic way by using the LeicaTM TruView plug-in, which manages laser scanning data plus high definition images and allows georeferenced representation of the fractures. After GIS processing and additional in situ engineering-geological surveys, data were used to create a 3D virtual reality illustrating the deterministic fracture pattern and properties of the single discontinuities. The detailed documentation of the geomechanical and geostructural characteristics of the discontinuities was subsequently used to perform numerical modelling analyses, aiming to obtain useful indications of likely stress conditions. Results can be used to improve optimisation of the excavation activities, taking in consideration the effects of local variation of the stress which is primarily reflected in situ by observed fracturing.