Update of Span Design Curve for Weak Rock Masses


Rimas Pakalnis, Thomas Brady,

A major focus of ground control research presently being conducted by the Geomechanics Group in the UBC Mining Department is to incorporate weak rock masses (RMR <50) into existing empirical design relationships. An emphasis is being placed upon the updated span design curve/critical span graph originally developed at UBC. The original database has been augmented by mapping of mines such as the Stillwater mine (Montana), the Eskay Creek Mine (BC) and several mines in the Carlin Trend and other parts of Nevada. In addition, empirical relationships between span, RMR and support guidelines are investigated. The common factor in all the above mentioned mines is a weak back and/or walls. In most cases, the ore zone is the weakest rock unit and must be dealt with to safely extract the mineral bearing rock. This work attempts to provide rock mechanic tools that will enable a mine operator to make economic decisions that will also ensure a safe working environment.
Keywords: Empirical design, Span Design, Weak Rock Mass, RMR, Support Requirements