A Comparison for Shear Resistant Behavior of Joints with Rock and Spiral Bolts Installed—A Numerical Approach

Abstract

ABSTRACT Spiral bolt is recently developed to enhance the support capability and cost effectiveness of rock bolt type support, and previous studies show that pull-out strength of spiral bolt is superior to rock bolt owing to gearing effect of spiral shape, even though the spiral bolt has less cross sectional area. In addition to the axial reaction of rock bolt such as suspension of rock blocks, if rock block slides on joint surface, bolt should react on shear force. Many studies indicate that shear loading contributes significantly to failure, which implies that shearing behavior of rock bolt type support ought to be investigated. In this study, we made two different numerical model with single weak layer for weathered rock, soft rock and hard rock as base rock blocks: (1) cylindrical shape mortal with centered deformed bar rock bolt, (2) cylindrical shape mortal with centered spiral bolt (twisted flat bar). To investigate the effect of axial force of bolt on shear strength, numerical simulations were done for both with and without the initial axial force of bolts. The results shows that shear resistant behavior of spiral bolt for hard rock joint is slightly superior to the rock bolt, but shear resistant performance of rock bolt for soft rock and weathered rock is equivalent or slightly superior spiral bolt. Spiral bolt can be a good alternative to rock bolt as it shows high performance in both axial and shear behavior of bolts.