In this manual, mechanically anchored resin bolts are defined as headed, threaded bolts that use grout for primary anchorage, and utilize a mechanical expansion anchor for tensioning and initial anchorage. There are numerous variations of this bolt type (see figure), which all combine the excellent anchorage of grouted bolts with the quick installation time of mechanical bolts.
Mechanically Anchored Resin-Assisted Bolts often have the same installation problems encountered as with Mechanically Anchored Bolts; however, the inclusion of grout can make some problems more pronounced. The following is a list of the Mechanically Anchored Bolt problems that are the most typical when grout is used:
- Spinners-Anchor Will Not Set
- Bolt Bends On Insertion-Can't Insert
- Low Tension/High Torque
- Erratic Or Poor Tension/Torque
- Bolt Breaks On Installation
- Anchor Breaks On Installation
When these problems are encountered, first install several bolts out of pattern without grout. If the problem still occurs, then look up the problem in the Mechanically Anchored Bolts section and follow the procedure listed. If the problem does not occur when grout is not used, then the problem is likely due to one of the following causes:
- E.1 Bail/Support Nut Too Strong
- E.2 Bolt Insertion Too Fast
- E.3 Grout Lubricating Borehole
- E.4 Grout Cartridge Material Interferes With Anchor Performance
- E.5 Anchor design
Because of the difficulty in detecting the cause of installation problems and the numerous designs of systems available, it is often best to contact the manufacturers of the bolts and the grout when these problems become prevalent. The manufacturers have the most information regarding their products and most likely have encountered these same problems at another site.