Abstract: For a better understanding of the evolution mechanism of 3-D crack propagation in brittle rock mass, the mechanism of 3-D crack propagation, coalescence and overlap in rock-like materials (a newly developed resin) with pre-existing double flaws under uniaxial compression is investigated based on the discrete element theory. Meanwhile, measurement circles are employed to monitor the variation of stress field of the model at different loading stages. The results reveal that wing cracks initiated from the long shaft ends of the pre-existing flaws C1-E and C2-W propagate towards the vertical direction of flaw plane to a certain length and then remain unchanged for a long time, and continue to propagate along the direction of the maximum principal stress when the stress reaches the peak. When axial stress reaches around the peak, petal-like wing cracks and reverse-wing cracks at the ends of the pre-existing flaws C1-W and C2-W coalesce and form a curling surface. As the axial stress increases to the vicinity of the peak, the maximum principal stress is mainly distributed in areas away from the pre-existing flaws, while the compressive stress is concentrated in the central region of the pre-existing flaws, thus imposing restrictions on the further propagation of the wing cracks. The maximum compressive stress and shear stress increase with the increasing strain while the maximum tensile stress drops near the peak stress, indicating that the crack propagation is mainly controlled by the compressive shear force in the later stage of loading.

Key words: 3-D crack propagation, compression test, discrete element method, stress field, measurement circle