Numerical simulation of fully encapsulated rock bolts with a tri-linear constitutive relation

摘要

This paper modified the original structural elements of pile in FLAC3D to analyse the performance of rock bolts. For the contact surface between the bar and the binding grout, bonding behaviour was modelled using the trilinear constitutive relation. Pull tests were used to testify the effectiveness of the modified pile elements. A satisfactory correlation was acquired between the modelling and physical results. This testified that the improved pile elements can successfully analyse the performance of bolts. Then, a numerical coal roadway was established and reinforced with the modified pile elements. After equilibrium, a non-uniform force distribution occurred along bolts. The axial force around the middle was maximal and the tensioning force at two ends of the bolt was minimal. A parametric analysis was performed to analyse the effect of relevant factors on performance of bolts. The results showed that with the bonding strength of the bolt surface raising, the neutral point shifted towards the excavation direction. Moreover, when the applied vertical stress was beyond a limit, the axial force in the bolts installed in the roadway side reduced dramatically. However, for the bolts installed in the roof, the axial force in the bolts was still raising.