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Significance of Bolt Tension in Ground Control.

Paper in Rock Support in Mining and Underground Construction Balkema PP 439-449 :439-449
Bolt installation tension is considered to be one of the most important factors contributing to rock reinforcement when mechanically anchored roof bolts are used. To evaluate the influence of uniform tensioning on roof stability, 13,000 mechanically anchored roof bolts were installed in an operating coal mine using both a conventional and a thrust-torque-controlled bolting machine. Geological and mine conditions were monitored when the bolts were installed and for 2 months afterward, and limited monitoring of roof sag, bolt tension, and changes in entry stability continued for another 4 years. Eleven of 24 variables were quantified and statistically analyzed for significance and correlations; the important bolting variables influencing roof sag were coefficient of variation of bolt tension and standard deviation of bolt tension. Long-term monitoring gave inconclusive results regarding bolt tension reinforcement mechanisms at this site. Other studies in highly stressed or weak ground have confirmed the importance of bolt tension in rock reinforcement. These studies are being integrated to develop criteria for primary support selection.
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OP 131-92
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Paper in Rock Support in Mining and Underground Construction. Balkema, PP. 439-449