For the mode I rock fracture toughness measurement, three standard methods have beenrecommended by the ISRM, but there has not been a standard method for the determination of mode II and mixedmode I-II rock fracture toughness. However mode II and mixed mode I-II fracturing of rock structures is morecommonly observed than mode I in various geological and structural engineering settings. So it is of greatimportant to thoroughly research these rock fracture problems and establish a standard method for determining themode II or mixed mode I-II fracture toughness for rock materials.rnBased on the progress made for mode I rock fracture research, the cracked chevron notched Brazilian disk(CCNBD) specimen was also introduced for mode II and mixed mode I-II rock fracture toughness measurement.When the crack is orientated at an angle with respect to the diametrical loading, the crack of the CCNBD specimenis exposed to the mode II or mixed mode I-II stress distribution conditions. The solutions for stress intensityfactors in the vicinity of the crack tip have been evaluated by the stepwise superimposition technique. In order tomake sure that the theoretical analysis is correct, numerical calculation method has been employed to calibrate thetheoretical results. It has been proved that the theoretical results yielded by the dislocation method are correct andreliable.rnAccording to the characteristic that the propagation of the crack in the CCNBD specimen is in its own planeand application of the energy superposition principle, the stress intensity factor of the mixed mode I-II has beendefined in dimensionless terms as Y≠mix = [(Y1*)2 + (Y*11)2]1/2. It was found that the curve of Y*mix was concave. Thereexists a lowest point which corresponds to the maximum external load and indicates the crack has reached itscritical state. Since the values of Y*mix, Y*1 and Y*II are only dependent on the specimen geometry(α0, α1, αB and θ), the critical values of Y*mix, Y1* and Y*II can be to known as long as the CCNBD specimen isprepared ready. It is only necessary to record the maximum load during the fracture tests.rnThe fracture locus is very useful to know whether the crack in a rock structure has reached its criticalcondition. According to the amount of practical fracture testing data obtained, the rock fracturing locus was foundto be(K1/KIC)3/2+(Ku/kuc)3/2 =1 and the S-critical criterion was found to be more suitable for rock mixed mode I-IIfracturing assessment.