Abstract: Researching the mechanical properties and failure mechanism of rock-bolt interface is of great significance since sliding between bolt and rock is a major failure form of anchorage system. With the microscopic bond
model proposed by one of the authors previously, the pull-out test of rock bolts was simulated using discrete element method (DEM). The complete load-displacement curves, the distribution of axial force and the interfacial shear stress were investigated, respectively. Furthermore, the microscopic failure mechanism of bolt-rock interface was analyzed according to the type and fabric of broken bonds. Research results are concluded as follows: 1) the simulated load-displacement curves were consistent with those from laboratory tests; 2) with the increase of anchor length, peak load value increased while average cohesive strength of anchor interface decreased; 3) progressive failure occurred in the anchor interface after pull load reached peak; 4) on macroscopic level, the failure of anchored segment exhibited as interface sliding; whereas on microscopic level, the failure manifested as the tensile failure of bonds near interface and the propagation of micro-cracks along the direction of axial force.

Key words: rock bolt, pull-out test, anchor interface, sliding failure, discrete element simulation