On the question of original versus modified stability graph factors – a critical evaluation

The Stability Graph has become an industry standard for open stope design. To date, there are two schools of thought on the use of the Original and Modified Stability Graph number factors. This paper is aimed at answering the question: Is there a difference between the Original and the modified stability number factors? To answer this question, a critical examination of the Extended Mathews and Modified Stability Graph databases was conducted to create a combined database of 316 datapoints. One version of the database was based on the original number factors, while a second was based on the modified factors. Logistic regression methods were applied to redefine the stope stability state boundaries. We concluded that differences between the stope stability states transition zones in the Stability Graphs are due to the differences in size of the databases rather than differences in the Original and Modified Stability Graph number factors.