Bearing plates have a dual purpose: as well as acting as a reaction surface to material moving against the head of the plate, and it secures and transfers load from any facing system into the rock bolts.
Size and thickness of the head plate need to be determined during the design phase as each project requires a different plate and it should not be assumed that they are standardized parts. However, for rock bolting, plates tend to be smaller but thicker as bearing failure below the plate is rarely an issue.
In order to transfer load from the rock bolt to the face efficiently, the plate should be secured tight to the face using a domed or hexagonal load nut. If a specific torque value is stated in the design, all nuts should be correctly tightened. If no load is stated, then a nominal figure of 10kN/m should be adopted to ensure that all nuts are tightened to a consistent amount.
Rock bolt/head plate articulation needs to be provided to ensure that the plate can be secured flush with the rock face. Articulation is the movement between the plate and the rock bolt; different plates can increase or decrease the amount of articulation. Insufficient articulation will cause the outside surface of the bar to clash with the inside edge of the bearing plate before the plate has come into contact with the rock face.
DYWIDAG-Systems International provide different plate types to provide increasing amounts of articulation. This range ensures that every project can be catered for.