ADDRESSING RESIN LOSS AND GLOVING ISSUES AT A MINE WITH COAL ROOF

Over the last year, Jennmar has been supplying roof bolts to a new mine with a thick coal roof in which massive resin loss was being measured. After trying various drill hole diameters, bolt profiles and available viscosities of resin, the mine still did not achieve their designed 90% encapsulation which meant an extra two bolts per metre were being installed. Over-coring to determine where the resin was going revealed that near vertical coal cleat was filling with resin but it also revealed that bolts were gloved for over 50% of their length. Extensive in situ testing achieved some interesting new data applicable to that mine site: 1) short encapsulation pull testing of gloved sections of bolt gave similar bond strength to the non-gloved bolts; 2) high viscosity (thick) resin gave improved encapsulation and 3) gloving could only be significantly reduced by a modified bolt end that nearly contacted the side of the bolt hole. Testing methods and results achieved along with comparing them to methods and results from previous literature on roof bolt gloving investigations are reported.