Abstract: Field practice demonstrates that geological discontinuities such as joints, weak intercalations, as well as faults, are a key factor controlling result of presplit blasting operations. The influence of angle of geological joints is investigated using the software LS-DYNA 3D. The numerical simulation of the process of presplit blasting in jointed models shows that the existence of the joint in rock mass can affect presplitting blasting significantly. The joint absorbs stress wave energy and prevents the transmission of stress wave, also impacts presplitting fissure occurrence. The cracks near joints mostly run along the direction vertical to the joints and gradually connect with the joints. When the angle between joint and the direction of designed presplit is small, the zigzag-shaped cracks are likely to rise, but hardly to penetrate. With increase of the angle, the effect of the stress wave transmission over the joints, as well as the particle vibration velocity near the joints can increase, and the produced presplitting cracks are more likely to straightly penetrate from one to another along the designed presplit line. When the joints and the designed presplit line are perpendicular to each other, the stress wave transmission over the joints reaches maximum and the cracks are likely to be in the same line connecting the presplit holes. Thus it becomes less possible for the zigzag-shaped crack to occur. The effect of presplitting to crack occurrence is best

Key words: presplitting blasting, jointed rock, numerical simulation, cracking from presplit blasting, stress wave