Control technology and failure types of anchor bolt support and U-steel frame support

The problem of high geo- stress and strong mining disturbance accelerated the failure of supporting bolt system and U- steel frame in coal mine roadway with the increase of mining depth. Based on theoretical analysis and field research, this paper divided U-steel frame into seven types which were in-plane structure failu re, joint tearing breakage, clamp failure, tie-rod and back-plane failure, axial force inducing breakage, deviating force inducing failure, multi-mechanism inducing failure. As for supporting bolt system failure, we classified it as debonding failure, surrounding rock failure, bolt fracture, surface protecting components ailure. Further, we pro posed three technologies including optimization of U- steel frame specification, backilling behind frame, structural reinforcement with bolt and cable on weakness part, to avoid the failures of U-steel frame. Meanwhile, we posed four technologies which were bolt reinforcement, performance improvement of surface protecting componen ts, improvement of resin anchoring agent, surrounding rock delayed grouting, to avoid the failures of supporting bolt system.