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The development of cone bolts is briefly reviewed in this paper. It was found that local bonding between the bolt and the grout can prevent the cone from moving and effectively absorbing dynamic energy. To solve the debonding issue and provide consistent performance of modified cone bolts (MCB), we developed a new patented debonding agent in the form of a plastic sleeve installed over the shaft of the cone bolt. Dynamic and static laboratory testing combined with in situ pull tests confirmed the new system's functionality. Drop tests confirmed that this new debonding agent is much more effective than grease used in the original cone bolt design. In addition, the new cone bolt is designed for 33 mm boreholes and thus can be used in a onepass rock support system to facilitate rapid drift development in underground mines. The new fully debonded MCB33 cone bolt is characterised by higher dynamic energy absorption capacity, consistent performance, and the ability to withstand repeated impacts from sequential rockburst events.
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Cai et al. (2010) studied this question.
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