This paper presents an experimental research on the length and shape of the fracture process zone of rocks under mode I, mixed mode (I + II) and mode II loading conditions for different geometries of cracked specimens made of two types of rocks, using the digital image correlation approach. Single edge notch bending (SENB) and semi-circular bend specimens are the two geometries considered. In order to investigate the effect of the specimen size on the fracture process zone length, rocks with three different sizes are produced and tested. To investigate the effect of the mode mixity on the fracture process zone length of marble and sandstone, the specimens are tested under different modes of loading. According to the experimental results, it is found that the fracture process zone length changes with mode ratio, specimen size, geometry and the material properties. The fracture process zone length increases when the mode of loading moves from mode I to mode II. Experimental results also show that fracture process zone becomes longer for specimens with larger sizes. The fracture process zone is also affected by the specimen geometry.
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