Study on the Estimation of the Axial Resistance of Spiral Bar Based on Interaction with Ground

Steel wire, which gives a pre-stress to ground and steel bar such as a rock bolt, are generally used in order to support rock. In this study, we introduce a new type support instead of the former one, like a rock bolt and cable bolt. We call spiral bar the bar that give torsion to the steel plate. It is easy to use the spiral bar like rock bolt, since it has high pullout resistance from ground. If axial force acts on the spiral bar, inner force will arise in borehole because of the spiral shape when grouting or a filling material fixes it. The behavior in the case that the spiral bar receives external axial force was investigated experimentally. And the 3-D numerical analysis was then performed by the finite difference method. A simple equation to estimate axial resistance of arbitrary sized spiral bar with self-enhancement function is proposed. The result of estimation is agreement with one of the experiments and numerical analysis.