A New Criterion for Numerical Modelling of Hangingwall Overbreak in Open Stopes

Abstract

Determining stability, quantifying planned dilution, and estimating the potential dilution associated with hangingwall overbreak are critical in the process of stope design in sublevel open stoping mines. To satisfy these objectives, empirical stability graphs and numerical modelling are currently used in the mining industry. Empirical methods are limited to the database used to calibrate them. In the case of numerical modelling, some of the available criteria used to evaluate hangingwall overbreak do not include the intermediate principal stress around the stope and/or the rock mass geotechnical characteristics. In this study, a new criterion for numerical modelling is proposed to estimate the hangingwall overbreak in open stopes. This new criterion includes the intermediate principal stress around the stope and the rock mass geotechnical characteristics. To develop the criterion, several open stope numerical models are simulated considering different geometrical and geotechnical conditions. The criterion is calibrated to reproduce empirical case histories of hangingwall overbreak. Next, the criterion is verified with case histories of hangingwall overbreak that presented different conditions used to calibrate the criterion. The proposed criterion establish a significant influence and relationship between rock quality and the minimum and intermediate principal stresses on hangingwall overbreak. The criterion offers sufficient flexibility for application to a wide range of geometries, in situ stress conditions, and depth and rock mass properties.