Anchorage and shear strength properties for composite tendons used in earthwork support systems

When employing advanced excavation techniques (e.g. continuous mining methods, mechanized tunnelling, etc.) it may be often necessary to excavate through previously supported areas. This means that the cutting heads of the excavation machine have to come into contact with supporting elements. In such situations, use of conventional steel support systems may damage the cutting bits of the machine, and thus, the support system must have the ability to be cut by standard cutters. As an alternative, composite tendons have the potential to be used as a support system in such conditions. The advantages of this type of bolts are; their cuttability, resistance against corrosion, and increase in rate of installation due to their lighter weight. The aim of this study is to explore the potential for use of composite tendons in situations that automated excavating techniques are to be used in grounds previously supported. As part of a research project with the Amirkabir University of Technology, a literature survey was conducted to explore the possibilities of the use of composite material as a support system in underground infrastructures. Secondly, the results of experimental study conducted by the author on two types of composite tendons are presented. Moreover, experiments were carried out on resin, as grouting material, and a summary of test results are presented. The experimental findings show that Weldgrip tendons have a very good capacity under shear loading. Also Weldgrip outer surface profile provides good pull-out strength as well as high residual load-bearing capacity.