THE USE OF THE CRACKED BRAZILIAN DISC GEOMETRY FOR ROCK FRACTURE INVESTIGATIONS

The cracked Brazilian disc geometry is receiving attention for rock fracture mechanics research due to its many advantages over other conventional geometrical configurations. A thorough study of the geometry is vitally important at this stage. A superimposition technique is presented to accurately solve the general cracked straight through Brazilian disc (CSTBD) fracture problem using the dislocation method and also the complex stress function method. The solution is valid for any crack inclination angle and any crack length. The solution for the a cracked chevron notched Brazilian disc (CCNBD) is then discussed. The theoretical evaluation for the Mode I cracked Brazilian disc fracture problem, a special case of the general problem, has been numerically calibrated by both finite element and boundary element methods, and a simple and accurate method to calculate the Mode I critical (minimum) dimensionless stress intensity factor for the CCNBD specimen is given. The valid geometrical range and valid minimum specimen size for the CCNBD geometry is presented to allow a valid Mode I fracture toughness value to be determined. The theoretical and numerical solutions for the stress intensity factor and the valid geometrical range are also substantiated by extensive experimental validation by comparing the results with those obtained by the ISRM-suggested CB and SR methods.