Dynamic Model and Mechanical Properties of the Two Parallel-Connected CRLD Bolts Verified with the Impact Tensile Test

Abstract

Dynamic model was theoretically established for the two parallel-connected constant-resistance-large-deformation (CRLD) bolts, and the theoretical results were experimentally verified with impact tensile tests on the CRLD bolts samples. The dynamic responses of the double CRLD bolts were investigated under the impact loads with different intensities. The theoretical analyses showed that (1) under relatively small loading the CRLD bolts deform elastically and the deformation finally returns to zero and (2) under the high impact load, including the stable impact load and unstable impact load, the CRLD bolts export structural deformation after the initial elastic deformation. The deformation of the bolts eventually stabilizes at a certain amount of the elongation caused by the relative sliding of the sleeves and rebars. The essential difference between the stable impact load and unstable impact load is that, under the stable impact load, no structural deformation will occur after the impact load ends; under the unstable impact load, the structural deformation will still occur after the impact load ends. The obtained results are of theoretical implications for rock support design with CRLD bolts under the dynamical loading condition.

An Insight from Rock Bolts and Potential Factors Influencing Their Durability and the Long-Term Stability of Deep Rock Tunnels

“…By this way, tunnel convergence is considerably influenced by creep [99,100]. Creep, considered to be a huge consistent deformation, is almost inevitable due to the high in-situ stresses and difficult geological conditions at great depth [101,102]. More precisely, it is a pervasive character of all types of rocks subjected to long-term loads [88].…”

Investigation of the evolution and control of fractures in surrounding rock under different pressure relief and support measures in mine roadways prone to rockburst events

“…Wu et al [29] and Kang et al [30] assessed the response of rock bolts under dynamic and static loads in coal mines under impact, and several series of high-strength rock bolts were developed with different rock bolt strengths, elongations and impact toughnesses. He and co-workers [31][32][33][34][35] developed constant resistance large deformation (CRLD) bolts and established a dynamic CRLD bolt model. An anchor cable that exhibits a high constant resistance and large deformation produces instantaneous deformation under dynamic loading; this cable has special mechanical properties and can maintain a constant resistance.…”