Interaction between rock bolt and rock bridge under tensile loading

The objective of this study is investigating the effect of loading rates on the interaction between rock bolts and rock bridges using experimental test and numerical simulation. A new test set up was developed experimentally for determination of tensile strength of bridge area. A concrete block with dimensions of 15 x 15 x 10 cm consisting non-persistent notch was prepared and subjected to tensile loading using special loading set up. The configuration of non-persistent joint was different in various samples. A 30-ton hydraulic load cell applied tensile loading to concrete complex with a high-pressure rate of 0.01 mm per second. Simultaneously with experimental test, numerical simulation was performed on the tensile behavior of non-persistent joint adjacent to rock bolt. Two sets of non-persistent joint were prepared. The first sets were similar to experimental one while, in the second sets, two edge joints with lengths of 1.5 cm, 3 cm and 4.5 cm were prepared. The angle of these joint related to horizontal axis were 0, 15, 30, 45, 60, 75, and 90. Also, the rock bolts adjacent to joints were simulated and were subjected to tensile loading with two high and low loading rates i.e. 0.01 mm/sec and 0.0001 mm/sec. The results showed that the crack propagation angle related to tensile load direction was decreased by decreasing the tensile loading rate. The tensile failure stress decreased by presence of pre-existing crack within the model. Tensile failure stress had minimum value whenever the angle of pre-existing crack was 0o. The numerical results were in a good accordance with experimental ones.