There are three cutting methods commonly used in tunnel blasting excavation: oblique cutting, straight cutting and mixed cutting.
Oblique cutting is divided into unidirectional cutting, wedge cutting, double wedge cutting and conical cutting. Oblique cutting is suitable for all kinds of dry rocks. The included angle between the gun coat and the working face is 55 ~ 70. The harder the rock, the smaller the included angle. The distance between each eye is 300~500mm, and the hard rock is small. The fundus is 200mm deeper than other holes, and the distance between each pair of eyes is100 ~ 200 mm. If it cannot penetrate, the hole will be cut once.
Straight cutting is divided into straight cutting, diamond cutting, cylindrical cutting and spiral cutting. The empty hole is set as the free surface in the straight cut, and then the holes adjacent to the empty hole are detonated in turn and gradually expanded. When it expands to 400~800mm, it becomes a free surface that is enough to assist the eye shape.
Mixed cutting is a mixed arrangement of straight cutting and oblique cutting, which is essentially straight cutting, but oblique cutting is used when expanding the groove. This can reduce the drilling workload, increase the angle between the oblique eye and the working face (generally 75 ~ 85) and overcome some shortcomings of the oblique eye cut method.