Empirical Approach for Weak Rock Mass

2003

Thomas Michael Brady, Lewis Albert Martin, Rimas Pakalnis,

This paper describes the application of empirical approaches as applied to weak rock masses. The original database comprising most of the empirical design relationships presently employed in hard rock mining operations has been derived from fair to good quality rock masses which exhibit an RMR76 in excess of 50% or Q values of 2.0 or greater. A major focus of research presently conducted by the Spokane Research Laboratories of NIOSH is to augment existing design relationships to incorporate weak rock masses such as are associated with the Nevada – Carlin operations. The “Span Design Curve for Man-Entry” mining has been augmented for rock qualities ranging from RMR76 values between 20-50%. The failure mechanism as observed and the support implemented to confine the potential instability as related to the rock quality is summarized along with the methods of extraction. The paper will introduce research being conducted at NIOSH/UBC where relationships between weak rock quality and support potential, stope design (Stability Graph),mining method among other observations are made for mines throughout North America. The commonality of all the mines within this database is the weak back or wall that operators have to access ensuring a safe and cost effective operation under controlled conditions. This work attempts to provide tools for the operator to make decisions in terms of providing a safe working environment.

Keywords: Rock, empirical, curves, mass, Design, span, weak, rating