Development of a novel energy-absorbing bolt with extraordinarily large elongation and constant resistance

Abstract

This paper presents an innovation work on the development of a novel energy-absorbing bolt characterized by an extraordinarily large elongation and high constant resistance. The bolt has a compound structure consisting of a cone-like piston sliding inside an elastically-deformable sleeve pipe. The frictional resistance generated by the sliding of the cone body relative to the internal surface of the sleeve pipe was mathematically formulated which is dependent on the elastic property of the sleeve pipe, the geometry of the cone and the frictional properties of the sliding interface, and independent of the external loads under the static loading conditions. A dashpot element for the cone-sleeve relative motion, termed “stick-slip element”, was proposed in construction of the lumped-mass model of the bolt for development of the constitutive equations that exhibits a frequency-dependent frictional behavior and a stick-slip oscillating response. The results from the static pull tests compared very well with the predicted working resistances, energy-absorbing capacity and elongations. The time-marching scheme of the bolt׳s impact load from the weight-dropping tests evolves with the pulsation response in the initial phase, stick-slip oscillation in the subsequent regime over which the dynamic energy is consumed, and a quasi-linear attenuation in the later phase. It demonstrates the fact that this bolt is robust in damping the dynamic load. The analytical work in this study provides solutions in the assessment of the large deformation and establishment of the forewarning precursors associated with deep mines.