Investigation of different types of flexible anchor tendons (rock bolts) for stabilization of rock masses

Conclusions

• 1. On the basis of tests, several types of flexible prestressed anchor tendons with tensions of 100–190 tons and embedment lengths of up to 40 m were recommended and experimentally justified for strengthening potentially unstable rock. Their basic constructional and technical parameters were determined, and their economic indices were calculated.

• 2. The most promising type of anchor is the flexible prestressed anchor tendon made from a bundle of parallel high-strength 5-mm diameter wires, which develop a maximum force in the hole. The strand and rope anchor tendons require a smaller volume of labor, but the wires in the strands and ropes undergo torsional and bending forces which cause large stress losses. Stabilization of the stresses in a cable requires a long time, making it necessary to apply either tensioning or preliminary elongation.

• 3. Further improvement in the different types of prestressed anchor tendons should be carried out by using high-strength wires 7–8 mm in diameter, with a strength of 170–200 kg/mm², which are being produced now on an industrial scale. It is necessary to enlarge the tendons, thus increasing their capacity, and to improve the techniques for their fabrication and for the mechanization of their installation.