Micro-mesoscopic test on fracture failure of intensive rock bolts

Comprehensive test methods of chemical composition analysis,mechanical properties test,SEM and metallo- graphic microscopy were used to analyze the frequent fracture failure of rock bolts whose yield strength exceeded 500 MPa. The reasons of fracture failure were preliminarily revealed from micro-mesoscopic mechanism angle com- bined with actual stress characteristics and theories of fracture failure analysis. The results showed that intrinsic attrib- utes such as material and manufacturing deficiency were internal factor,while working environment,stress corrosion and complex stress state were external factor. The ductility of rock bolts determined the fracture mode and morphology. Comprehensive methods including improving stress state,full-length anchored,optimizing contour of rock bolts and an- ticorrosion processing were put forward to reduce the probability of fracture failure.