Abstract
Bolt installation quality is influenced by various factors, some are well known and others are less recognised. A programme of field and laboratory studies was undertaken to examine various factors of relevance to the load transfer mechanism between the bolt, resin and rock to ensure test methods truly represent field performance. Short encapsulation tests were undertaken as part of the Australian Coal Association Research Program (ACARP) funded project (C21011) with the ultimate aim of developing standard test methods for assessing bolt encapsulation with chemical resin anchor installations. The field study consisted of a series of Short Encapsulation Pull Tests (SEPT) carried out in three mines with different geological conditions to determine the most representative and practical method of SEPT. Additional field work included installation of bolts into threaded steel tubes for subsequent removal and laboratory evaluation. A series of pull tests was carried out by installing bolts in overhead rig mounted sandstone block, cast in concrete with controlled encapsulation length. Factors of importance considered included; borehole diameter, resin annulus thickness, installation time (including bolt spin to the back and “spin at back”), the effect of gloving and hole over drill. It was found that the borehole diameter had a detrimental effect on the encapsulation bonding strength. Bolt installation time of approximately 10 s constituted an acceptable time for effective bolt installation and within the resin manufacturers recommended time of 14 s. Maintaining constant length of encapsulation was paramount for obtaining consistency and repeatability of the test results. Finally, a numerical simulation study was carried out to assess the capabilities of FLAC 2D software in simulating the pull testing of rock bolts.
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Acknowledgments
The research project has been funded by the Australian Coal Association Research Program (ACARP), project C21011. The cooperation of the personnel at Baal Bone, Tahmoor, Gujarat NRE No. 1 and Springvale Mines is gratefully acknowledged. Also thanks to Jennmar Australia for providing bolts and assistance in field trials, and Minova Australia for providing resins and expertise on resin usage and preparation of the cast samples. Special thanks to the School of Civil, Mining and Environmental Engineering, University of Wollongong for excellent support, in providing the technical staff, and excellent facilities to enable the research team to undertake laboratory studies of the project.
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Aziz, N., Craig, P., Mirzaghorbanali, A. et al. Factors Influencing the Quality of Encapsulation in Rock Bolting. Rock Mech Rock Eng 49, 3189–3203 (2016). https://doi.org/10.1007/s00603-016-0973-5
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DOI: https://doi.org/10.1007/s00603-016-0973-5