Video of a twisted yeildable bolt driving into a rock hole
This video shows the process of 23-degree twisted rock bolt (TYB) driving into a hole with 25 mm diameter. TYBs were made of low-alloy steel of 09G2C grade having yield strength 325 MPa, tensile strength 470 MPa, elongation 21% and impact toughness 59 Дж/см3. Uniaxial tensile strength of the rock was 42.3±3.6 MPa and elasticity module 14 GPa. TYB cylindrical rode had diameter 20 mm. The rod had two feathers 3 mm high. The feathers cut the 0.5 grooves. A pneumatic hammer was used to drive the bolt. The hummer had a ring piston, inner channel and a clamp. The bolt was inserted into the channel and fixed with the clamp. The rod bolt was marked with a chalk every 10 cm.