The creation of a solid base for mining engineering requires an explicit distinction between two important notions, namely geological and geotechnical models. The geological model provides a three-dimensional view of the geological structure of the earth. In turn, the geotechnical model defines certain mechanical properties for the geological formations. As a result, both models minimize financial and safety risks related to uncertainty below the surface (Zhou & Guo, 2020).
The process of creating a geological model begins with an extensive amount of data collection, which entails core drilling, mapping the surface, and the analysis of large areas of hydrogeology. Current techniques gradually move toward being multidisciplinary, combining traditional well-logging methods with geophysical data. Such a combination allows mining engineers to define the structure of a mineral deposit in detail, showing its lateral lithological variability and complicated fault systems before the start of any digging (Charbaoui et al., 2023).
Once the geological structure has been described, engineers create the geotechnical model using the physical and mechanical properties of the described formations. Even though the classical method included expensive core sample laboratory tests, nowadays, the automation of geotechnical characterization through geophysical logging is widely used. Rock density and uniaxial compressive strength can be accurately determined through sonic transit time. This data is then spatially interpolated to produce three-dimensional geotechnical block models (Zhou et al., 2001).
These models become the basis for further engineering calculations. In the case of an open pit mine, the geotechnical model determines the safety limits of the angles of pit slopes and their design. For an underground mine, this means proper stoping sequence, pillar size, and necessary support measures. Evaluating the rock-mass response with respect to these designed structural elements determines the success of the whole mining operation (Elmouttie & Dean, 2020).
However, the creation of such models is a gradual process that does not end with the initial design of the model but extends throughout its lifetime as part of the mining operation. With further excavation and exposure of new rock layers, any existing structural hypotheses have to be constantly checked in accordance with the current state of affairs. The use of terrestrial radar, satellite interferometry, and piezometers provides consistent feedback from the field. It allows re-calibrating the model on the regular basis and thus recognizing possible slope instability (Elmouttie & Dean, 2020).
In summary, it is apparent that geologic and geotechnical modeling represent dynamic processes, which should be adjusted at the same time as the mining process. By utilizing the continuously updated information collected by field measurements at drill holes, modern geophysical methods, and monitoring systems, miners will be able to react to any changes in the properties of rock mass immediately. The maintenance of these dynamic models guarantees the engineering decisions made based on facts.
Image credits: SRK Consulting (Available here: https://www.srk.com/en/services/3d-geological-modelling)
References
Charbaoui, A., Kchikach, A., Jaffal, M., Khadiri, O. Y., Guernouche, M., Amar, M., Bikarnaf, A., Jourani, E., & Khelifi, N. (2023). New Insights from Geophysical, Hydrogeological and Borehole Data into the Deep Structure of the Louta Phosphatic Deposit (Gantour Basin, Morocco): Mining Implications. Geosciences, 13, 357. https://doi.org/10.3390/geosciences13120357
Elmouttie, M., & Dean, P. (2020). Systems Engineering Approach to Slope Stability Monitoring in the Digital Mine. Resources, 9, 42. https://doi.org/10.3390/resources9040042
Zhou, B., & Guo, H. (2020). Applications of Geophysical Logs to Coal Mining—Some Illustrative Examples. Resources, 9, 11. https://doi.org/10.3390/resources9020011
Zhou, B., Hatherly, P., Guo, H., & Poulsen, B. (2001). Automated Geotechnical Characterisation from Geophysical Logs: Examples from Southern Colliery, Central Queensland. Exploration Geophysics, 32, 336–339. https://doi.org/10.1071/eg01336
