Dynamic performance of energy-absorbing rockbolts based on laboratory test results. Part I: Evolution, deformation mechanisms, dynamic performance and classification

摘要

Deep mining and the related dynamic loading are the critical challenges confronting the reinforcement system like energy-absorbing rockbolts, which plays a decisive role in the dynamic response of underground mine excavations. Over the past decades, various types of novel energy-absorbing rockbolts with different deformation mechanisms and dynamic characteristics have been invented. Meanwhile, the test methods and facilities to quantify the dynamic performance of rockbolts have been proposed, and a lot of test results are obtained. In order to demonstrate the development of energy-absorbing bolts and their dynamic performances, and to reveal inherent features relating to the dynamic performance of rockbolts, these two companion papers are presented. Part I concentrates on the development, dynamic performance, and classification of energy-absorbing rockbolts. According to the energy absorption mechanism, the bolt can be divided into two behaviour modes. As for mode I, the bolts accommodate rock deformation and absorb energies via plastic deformation of the shank, and the representative bolts are D-bolt, MP1 bolt, PAR1 bolt and BHRB400/500/600. As for mode II, the energies are dissipated through ploughing of the anchor in the grout (e.g. Cone bolt, MCB, Durabar and Yield-Loc) or extrusion of the shank within the internal device (e.g. Garford, Roofex and He-bolt). According to varying dynamic capacities, the rockbolts are divided into low, medium, high and very high categories. The presented classification scheme facilitates the selection of rockbolts in the preliminary design stages and assists designers in adjusting the scheme during the operation based on field observations.