BOLT SYSTEM Kent McTyer1 ABSTRACT: Spin-to-stall resin bolting system originated in the late 1990’s at South Africa’s Goedehoop Colliery and has become accepted over recent years in Australian underground coal mines. The main benefit touted is a simplified installation procedure that can lead to both reduced bolting cycle times and more consistent installation quality. These benefits are consistent with mining industry requirements of greater overall efficiencies – especially in mine roadway development rates. Traditional pre-tensioned resin bolting practice has employed a bolt-rotation stoppage, or hold time, to allow the fast-set resin anchor to fully cure before re-starting rotation to pre-tension the bolt. Spin-to-stall bolting diverges from traditional methods by continuing to apply rotation until the bolt stalls. Continued application of rotation breaks the nut pin allowing the nut to run up the thread to produce pre-tension. While the simplified installation procedure is beneficial, concerns exist over the reduction in resin mixing time – especially at the top of the drill hole. Specifically, whether there is sufficient time for the resin to properly mix and attain full strength. Without full strength the resin anchor at the top of the bolt has reduced ability to transfer load – reducing the resin bolts effective length. This paper discusses some key resin mixing parameters and their effect on load transfer. These parameters were tested during the development of a spin-to-stall resin bolting system. The test methods simulate underground spin-to-stall installation practice. This assessment technique is thorough and provides industry with greater confidence when evaluating the performance of a spin-to-stall resin bolting system.