SCT Operations (Strata Control Technology)
  • Stuart MacGregor

Welcome to SCT's own publications library which contains a collection of recent publications and other resources with reliable research about our technology. 

  • Determination of Load Transfer Characteristics of Gloved Resin Bolts from Laboratory and In-Situ Field Testing - Stuart MacGregor - Published 2005

    Resin based grouts are the main form of rock bolt anchorage in the underground coal industry in Australia and New Zealand. To be effective, the system requires the mixing of the catalyst and mastic components of the resin, as well as shredding of the laminate cartridge that contains the resin.

    An unknown measure is the load transfer characteristics of a bolt where the resin is well mixed but remains encased in the cartridge (gloved). Laboratory and in situ field investigations have been undertaken to quantify the performance loss due to mixed gloved bolts. This work showed repeatable results, indicating serious performance loss of the gloved and mixed system, with load transfer approximately 10-15% of a non-gloved system (MacGregor, 2004).

    The in situ testing has demonstrated the relationship between the adhesion qualities of the resin and the mechanical interlock generated by radial confinement with progressively increasing tensile load. Effective load transfer is defined by the ability of the system to sustain shear stress on the bolt hole wall. Determination-of-Load-Transfer-Characteristics-of-Gloved-Resin-Bolts-from-Laboratory-and-In-Situ-Field-Testing-S.MacGregor.pdf1.3 MB
  • Instrumentation Monitoring at an Underground Mine to Establish Failure Mechanisms, Confirm Numerical Modelling and Determine Safe Working Conditions - Stuart MacGregor

    A number of potential failure modes were identified by observation and numerical modelling in the underground operation at Telfer Gold Mine. In order to gain a better understanding of the mechanisms of failure an instrumentation programme was designed. Monitoring methods included closure monitoring using tape, rod and sonic probe extensometers, stress monitoring, reinforcement monitoring with strain gauges, prism monitoring in the open pit and observation using a borehole camera.

    The results from the monitoring instrumentation established local and regional failure mechanisms with greater certainty. The information allowed mining methods, extraction sequences and reinforcement requirements to be reliably designed, using numerical modelling as a tool.

    Instrumentation was also installed to determine the ongoing stability of excavations which allowed safe working conditions to be identified throughout the mine. The aim of each type of instrumentation method is presented along with the interpretation of the monitoring results. The practical implications of each set of results are discussed and a cost breakdown for all the instrumentation types is included. Instrumentation-Monitoring-at-an-Underground-Mine-to-Establish-Failure-Mechanisms-Confirm-Numerical-Modelling-and-Determine-Safe-Working-Conditions-S.MacGregor.pdf2.2 MB
  • Investigation Into the Extent and Mechanisms of Gloving and Un mixed Resin in Fully Encapsulated Roof Bolts - Stuart MacGregor

    Effective strata control, utilising fully encapsulated roof bolts is dependent on the installed quality of the reinforcement elements. One mechanism by which roof bolts may become less than fully efficient is by glove fingering (gloving) and un-mixing of the resin. Following a routine installed bolt quality audit and some small roof failures containing gloved bolts, a work programme was initiated to determine the extent of the gloving and un-mixing problem and to develop an understanding of mechanisms involved. Results have shown that gloving and un-mixing is a systematic and widespread pheno mena, occurring across the range of resin and/or bolt manufacturers, and in a variety of roof types. Gloving was found in bolts installed using either hand held pneumatic or continuous miner mounted hydraulic bolting rigs, under run of mine (ROM) condition s by operators, and under controlled manufactures “best practice” conditions.

    The mechanisms involved have been confirmed as being the development of a pressure front as the bolt encounters the resin cartridge and is spun up the hole, which in turn, leads to over -pressurisation and radial expansion of the resin cartridge. The result is an increase in the diameter of the plastic cartridge. Allowing the bolt to be spun up inside the cartridge without making sufficient contact to shred the cartridge or the hardener envelope, typically resulting in a portion of the cartridge enveloping the bolt and unmixed resin mastic and catalyst.

    Once the mechanisms involved and extent of the problem became clear, further research was undertaken to assess alternative bolt profiles and modifications in an effort to minimise and/or eliminate the gloving and unmixing phenomenon. Research has been undertaken using recovered bolts from various mine sites, as well as test bench trials and the quantification of the loading characteristics of gloved bolts using strain gauge roof bolts.

    To understand the impacts of gloved and un-mixed bolts on roof control, failure pathways and reinforcement requirements a FLAC 2D numerical simulation was undertaken, with the results being incorporated into the strata management plan for a particular operation. Laboratory data has been collected and analysed to assess magnitudes of resin pressure as the bolt encounters the cartridge1 and the effects of gloving and un-mixing on the load transfer characteristics of the resin bolt system. Investigation-Into-the-Extent-and-Mechanisms-of-Gloving-and-Un-mixed-Resin-in-Fully-Encapsulated-Roof-Bolts-S.MacGregor.pdf502 KB
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