ABSTRACT:

Mining ground support systems typically include rockbolts, wire-mesh, and shotcrete or fibercrete. The selection and installation sequence of these products is determined by operational needs and ground support requirements. Without quantifiable performance data, finding the proper balance can be a challenge. In this study, mechanical testing is used to measure the relative performance of different installation sequences of mesh, bolts, and shotcrete. 6×6-ft, 4-inch thick shotcrete panels bolted on a 4×4-ft pattern were constructed to represent different installation sequence options, and tested in a specially constructed test machine to measure the force-displacement response during 10 inches of deflection between the bolts. Afterwards, post-bolted macro-synthetic fiber reinforced shotcrete was tested for comparison with the wire-mesh alternatives. Low (5-lb/yd3) and high (11-lb/yd3) fiber content mixes were tested. Lastly, the influence of external mesh was measured. The results demonstrate the importance of shotcrete in the overall support system, the benefit of post-bolting, and provide a direct comparison between mesh and macro-synthetic fiber reinforcement. The test results are coupled with empirical shotcrete design guidelines to provide recommendations for selecting appropriate surface support based on ground conditions. The overall goal of this work is to help match the right support for the ground conditions, thereby improving the safety of underground workers.

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