Influences of Loading Condition and Rock Strength to the Performance of Rock Bolts

The influences of displacing angle, joint gap, and rock strength to the performance of rebar bolts and D-Bolts are evaluated in this study. A new method was developed to apply pull and shear loads to the bolt specimen in any combination so that a displacing angle can be established in the range from 0 (pure pull) to 90° (pure shear). In the tests, five displacing angles, two joint gaps, and three “rock” materials were used. The tests showed that the ultimate loads of both the D-Bolt and the rebar bolt remained constant for all the five displacing angles. The deformation capacity of D-Bolt is approximately 3.5 times the rebar under pure pull and 50 % higher than the rebar under pure shear. Both D-Bolt and rebar displaced more in the weak “rock” (concrete) than in the hard rock. The ultimate load of the bolts slightly decreased in the hard rock at pure shear. The deformation capacity of the bolts increased with the joint gap. The energy absorption capacity of the D-Bolt is 3.7 to 1.5 times that of the rebar bolt, depending on the displacing angle. The bolts installed in weak concrete blocks absorbed more energy than those installed in hard rock and high-strength concrete blocks. The loading angle is increased by the displacing angle. These two angles can be calculated with each other in an analytical solution.