The stability graph after three decades in use: Experiences and the way forward

Abstract

The stability graph was introduced approximately three decades ago for open stope design. Since then, it has gained wide recognition in open stope design around the world in hard rock metalliferous mining. Several developments have taken place following its initial inception aimed at improving its reliability in predicting the stability state of open stopes. These developments include redefinition of the stability graph number factors, the transition zones and addition of new factors. Various types of stability graphs have also emerged over the years for other purposes such as cablebolt layout design. The original database has also been significantly expanded from the 26 cases in 1981 to 483 cases to date. This article critically reviews the developments of the stability graph to date with the objective of: (1) Synthesising the scattered knowledge of these developments in the literature to a single source. (2) Creating awareness among potential users of the method, of the problems and risks arising from the uncoordinated developments in the method and the consequences of the lack of consensus in the choice of stability number factors. (3) Identifying areas for further research to improve the reliability of the method. (4) Finally, providing guidelines to inexperienced users and practitioners unaware of the various developments on the stability graph on when to use any one of the several stability graph types currently available. The article stresses that as an empirical method, the reliability of the stability graph method is largely dependent on the size, quality and consistency of the database. Hence, there must be consistency in the determination of the stability graph factors and accepted stope stability state transition zones. The present tendency for authors to arbitrarily choose between the original and modified stability number factors result in incomparable data that cannot be combined, while the different transition zones result in different interpretations of the stability state of stopes. The review also shows that there is need for factors that account for stope stand-up time, blast damage and gravity factor that is stress factor dependent. There is also a need to develop procedures for determining stability of open stope surfaces that are made of backfill. The inexperienced user and practitioner unaware of the various versions of the stability graph should be conscious of the different versions and types of stability graphs to make the appropriate choice for his/her design. The stability graph should also be used with caution, when applied to narrow vein orebodies because no version of the graphs accounts for orebody thickness in the definitions of the stability states.

Stope Stability Assessment and Effect of Horizontal to Vertical Stress Ratio on the Yielding and Relaxation Zones Around Underground Open Stopes Using Empirical and Finite Element Methods

“…Today, the extended version of the method, given by (Trueman et al, 2000;Mawdesley et al, 2001), is based on more than 400 case histories collected from underground hard rock mines. A comprehensive review by (Suorineni, 2010) shows that there are some shortcomings with this method such as the need for factors that account for the stope stand-up time and blast damage. In addition, this method does not have procedures for determining the stability of stope surfaces made of backfill.…”

Statistical analysis of the stability number adjustment factors and implications for underground mine design

“…The most significant ones are 4 : the subjectivity in the definition of the stability zones, the absence of standardization of the extended database, 5 the non-representation of the rock stress factor, A, for instabilities caused by low confinement conditions, and the poor representation of the sliding failure modes by the gravity adjustment factor C. In the past three decades, several studies have addressed these limitations. Redefinition of the transition zones 2,6 and statistical analysis using a Bayesian likelihood statistic 7 have been proposed.…”

“…Four stability zones have been defined. 4 First, the Stable Zone represents the excavation which stand unsupported, or with localized support. Then, the Failure Zone represents the excavation where localized unravelling occurs, but a stable arch forms.…”

Gerenciamento de risco aplicado à diluição de minério

“…É esta correlação gráfica, que habilita a aplicação do sistema RMR ao dimensionamento de realces de mina (Bieniawski, 1989;Villaescusa, 2014 (Barton et al, 1974;Brady & Brown, 2004;Villaescusa, 2014 (Barton et al, 1974;Villaescusa, 2014 (Hutchinson & Diederichs, 1996). (Potvin & Hadjigeorgiou, 2001;Suorineni, 2010;Villaescusa, 2014).…”

“…Figura 2.26 -Gráfico de estabilidade modificado de Potvin (modificado de Potvin, 1988 refere-se apenas às condições intrínsecas ao maciço rochoso, não considerando condições circunstanciais presentes no mesmo, tensões e presença de água (Mawdesley et al, 2001;Potvin & Hadjigeorgiou, 2001;Suorineni, 2010 Tabela 2.3 -Relação entre o excesso de tensão e condição do maciço rochoso.…”