The excavation in conventional tunneling is typically supported by radial bolts, reinforced shotcrete and if required by steel arches or lattice girders. Radially installed bolts reinforce the surrounding ground and create a so-called
supporting arch around the excavation. Thus, radial bolts are an essential part of the primary support in tunnel construction and must be chosen carefully to suit the expected ground conditions.
There is no bolt covering all demands and therefore decision criteria are necessary to define the most suitable bolt type(s) at the design stage. This requires knowledge about various characteristics of bolt types,
installation methods, areas of application, ground conditions and activation modes. After the selection, individual types must be clearly defined in tender documents, so that both the contractor's offers are comparable, but also
the originally designed measures are installed during construction to ensure safe, stable, and cost-optimized excavation processes.
To enable this process, this document describes common radial bolt types, their characteristics and properties, advantages, and disadvantages as well as safety and quality concerns.