Unwedge is a limit-equilibrium (LE) analysis program, so bolts are converted to an equivalent support force that is added into the LE solution process. This process computes a factor of safety of the wedge using force equilibrium. It does not compute whether a bolt fails or not. So when you see a failure mode indicated, this does not mean that the bolt is failing. This means that if the bolt was to fail, it would most likely fail by that mechanism, and the available amount of support force is computed using this failure mode. For more information, see the Bolt Force Diagram section of the Online Help.
Bolt force diagrams are used in a LE analysis to determine the amount of force a bolt element can put back into the force equations used in the LE analysis. If the wedge has a factor of safety less than 1, then this infers that the support has failed. If the FS is greater than 1, then the support has not failed.
Unwedge considers six bolt failure modes: