Experimental study on tensile properties of high strength and high ductility tension-type bolt

Anchor bolt reinforcement is widely used in geotechnical engineering to mitigate deformation of rock mass weak structural planes, but conventional steels often sacrifice ductility for strength. This study proposes a novel tensile-type anchor bolt using high-strength, high-ductility twinning-induced plasticity (TWIP) steel. Via static tensile, anchorage performance, and pull-out tests, it compared TWIP with conventional steels (HRB400, HPB300, SUS304) in mechanical properties, anchorage, and shear stress distribution. Results show TWIP has 56 % elongation after fracture, 1032 MPa ultimate tensile strength, and 2.81 strength-to-yield ratio, outperforming traditional steels. A warm-upsetting process optimized anchorage (100 % efficiency). During the bolt pull-out test, the shear stress of the TWIP steel bolt is most evenly distributed along the length of the rod body, and there is no obvious stress concentration. TWIP bolts can still maintain residual stress during slipping delayed abrupt load loss even after interface debonding, showcasing superior anti-slip capability and energy absorption. This study provides a scientific foundation for the application of TWIP steel in anchor systems and offers an advanced technical solution to address rock mass instability.