Rock fracture toughness is a very important rock property used in many rock engineering applications. For its measurement cracked Brazilian disc is advantageous over other specimen geometries. The advantages include higher failure load, lower dispersion of test results, easier sample preparation and simpler experimental configuration. In addition the specimen geometry can be easily adapted to measure single mode or mixed mode fracture toughness. This book provides the background research work for the development of cracked Brazilian disc, including cracked chevron-notched Brazilian disc (CCNBD) and cracked straight through Brazilian disc (CSTBD), for Model I, Mode II and mixed Mode I and II fracture toughness testing. It gives insight to the third method for the measurement of Mode I rock fracture toughness suggested by the Testing Commission of the International Society for Rock Mechanics. It covers comprehensive theoretical analysis, numerical calibration and experimental validation of the testing method. The work presented in this book should provide a very useful reference to rock mechanics researchers and practitioners, as well as to rock engineering professionals.