Document Type
Conference Paper
Publication Date
2-2016
Abstract
Originating from South African practices, spin to stall bolting systems have seen an increasing focus within Australian coal mining operations over recent years. The primary driver for spin to stall applications is the goal of improved bolting cycle times, with a secondary benefit being simplified installation practices for roof bolting operators. These outcomes are seen as one part of a broader opportunity to improve overall underground mining efficiencies and extraction rates. Spin to stall bolting methods represent a divergence from long standing resin installation practices, with the resin ‘hold’ or ‘curing’ time being eliminated from the installation cycle. The bolt can therefore be spun continuously under thrust through the length of the resin cartridge, with rotation continuing until the resin polymer matrix cures and hardens, the bolt torque drive releases, the nut is advanced on the thread and the bolt is ultimately pre-tensioned until rotational stall of the drill rig motor occurs. However, concerns remain that as the resin cures under polymerisation, significant loading is immediately placed onto the resin matrix before the polymer chains have fully formed, with the subsequent risk of damage to the interfaces between the bolt, resin and borehole – ultimately weakening bolt load transfer into the strata. The divergence from standard resin bolting practices has also led to changes in product validation methods, with validation practices being created specifically for spin to stall testing. This paper provides a detailed analysis of the technical parameters that govern spin to stall installations, as well as an assessment of validation techniques, including the inherent difficulties associated with underground testing. The arising question is whether current validation practices actually address all aspects of bolt performance, with some areas for concern being potentially masked regarding bolt load transfer. Finally, this paper offers potential improvements for spin to stall validation methods, in an attempt to further progress this area of work within the industry.
Publication Details
David William Evans, Spin to Stall Bolting Systems–a Review of Validation Standards, in Naj Aziz and Bob Kininmonth (eds.), Proceedings of the 16th Coal Operators' Conference, Mining Engineering, University of Wollongong, 10-12 February 2016, 64-74.