What kinds of detonation sequences are there for open-pit blasting? What are the advantages and disadvantages of each?

Open-air blasting has the following detonation sequences:

First, initiate in the order of the line. Detonation in row order is to blast the blast holes arranged parallel to the top line of the step slope in the order of rows. The advantage of this method of detonation is that the blasting has a large forward thrust, overcomes a large chassis resistance line, and the blasting collapse line is obvious. The disadvantage is that the rock colliding and squeezing effect is small during the blasting process, which is not conducive to the rock fragmentation and the flat pile. Because of the excessive charge, it is easy to cause blasting earthquake damage.

Second, the slash line detonated. The segmented blasthole connection and the stepped top line are oblique detonation methods called slash detonation. Figure 1 (ɑ) is a diagonal form, often used under the condition that the step has a side free surface, and the angle between the blasthole connection and the top line of the step slope is generally about 35°. This blasting provides a wider free surface for the rear blast. (b) In the form of a wedge-shaped tongue and groove, used in trenching. (c) In the form of a trapezoidal groove, it is mostly used for the working surface. The advantages of slanting line detonation are: square and rectangular cloth holes, which facilitates the drilling, charging and packing operations. The mechanized slanting line detonation increases the adjacent coefficient of the blasthole, which is beneficial to improve the blasting quality, and at the same time, blasting the pile and reducing the workload of the shovel. Improve the efficiency of the shovel. Due to the large number of segments, the amount of charge per segment is small and scattered, so that the blasting earthquake is weakened, and the back and side impacts are small, which can alleviate the direct damage to the rock mass. The detonation network has various forms of variation, is flexible, and can be used according to various conditions. The changes have taken corresponding measures to meet the requirements of various blasting. The disadvantage is that the rear-row hole is more viscous, the collapse line is not obvious, and the blasting effect is affected. The construction and inspection of the segmentation operation are complicated, error-prone, and the detonation material is expensive.

Figure 1 oblique line detonation

1, 2, 3, 4, 5 ... - detonation sequence, A, B, C, D, E, F- front section is the free surface created by the latter stage of blasting

Third, the interval hole detonation. The interval hole detonation is to detonate the same row of holes in the order of parity.

Figure 2 (É‘) step mode, the blasting process is not only affected by many aspects of blasting, but also the time is long, greatly improving the blasting quality, the blasting concentration, the backlash side impact are small, Figure 2 (b) is wavy In the same way, compared with the sequential detonation, the front blasting creates a larger free surface for the rear blasting because the blasting quality is improved and the sag width and rush are smaller.

Figure 2 Spacer detonation

(É‘) step mode; (b) wave mode

Fourth, the linear groove is detonated. Straight groove blasting is the first use of dense blastholes arranged along a straight line to create a new free surface, generally used in trenches. The scheme is broken evenly, and the block is appropriate. The explosion pile is concentrated along the axis of the ditch, and there is no rock back. The main disadvantages are: the punching work is large, the amount of blasting is low, and the unit consumption is high. At the same time, the side of the groove is large and the vibration intensity is high.