Evaluation of the Stability of Underground Rock Pillars through a Probabilistic Approach

Problem statement: When the room and pillar mining method is adopted, the dimensioning of the rock pillars is one of the most important aspects that need to be faced from the engineering point of view. The available calculation methods are usually simplified and involve the areas of influence method for the evaluation of the mean axial stress induced in the pillar and the empirical formula to estimate the global strength of the pillar. Approach: A new probabilistic approach is proposed in this study concerning the evaluation of the degree of safety of a pillar, as far as rupture of the rock is concerned. This approach is based on the exact evaluation of the stress state inside the pillar and it takes into due consideration the typical uncertainty of the geomechanical parameters of the rock mass that makes up the pillar. Results and Conclusion: The pillar can therefore be dimensioned through an analysis of the cumulative probability distribution of the point safety factor in one or more points inside it.