Since the mining of Taihe Iron Mine, the continuous charging in the hole has been adopted, and the row is detonated in a row. The amount of a primer is large, and the height of the charge is low, resulting in a high block rate (more than 50%). In order to control the ore block rate and improve the blasting effect, the original blasting method was improved, and the bulk rate was effectively reduced.
First, the characteristics of the hole-by-hole detonation technology
The hole-by-hole detonation technique refers to the blasting of the blastholes in the same row in the blasting zone in accordance with the designed delay time. At the same time, the blastholes in the row of the blasting zone are sequentially blasted to the rear row according to another extension period, that is to say In the horizontal plane of the pre-explosion area, the blastholes in the horizontal row and the longitudinal column respectively adopt different delay times, but the blastholes usually located in one row or one column have the same surface extension time interval. In the two-dimensional plane, the detonation time of each blasthole is sequentially accumulated according to the length of the holes and the inter-rows, and each of them is detonated independently with respect to the surrounding blastholes. In this way, the blasting process advances in time and space according to a certain explosion isochronal line until the blasting process is completed. Compared with the multi-row hole differential detonation, the hole-by-hole detonation has the following characteristics:
(1) Firstly, the blasthole is created to create a free surface for the post-explosive blasthole. Increasing the free surface of the blasting can greatly increase the energy of the blasting explosive and improve the efficiency;
(2) The explosion stress wave is fully reflected along the free surface to strengthen the broken rock;
(3) The ore blasting of adjacent blastholes collides and squeezes each other to enhance the secondary crushing of the ore, which can reduce the blasting block degree, the large block rate is low, and the secondary blasting amount is small, which can greatly improve its subsequent work (shovel Loading and transportation) efficiency;
(4) At the same time, the amount of explosive charge is only a single hole charge, and the amount of primer is small, which can effectively control and reduce the occurrence of damage such as seismic waves, shock waves and flying stones.
Second, the design of the blasting parameters of the detonation by hole
Taihe iron ore is mainly drilled with KQ-200 type down-the-hole drilling rig . The diameter of the hole is 220mm. It adopts two kinds of triangle and square cloth holes. It uses mixed emulsion explosives and uses 2 # rock emulsion explosive to make the explosive charge. The blasting parameters are shown in Table 1.
Table 1 Explosion parameters
Drilling diameter (mm) | Step height (mm) | Hole depth (m) | Drilling angle (°) | Pitch (m) | Row spacing (m) | Resistance line (m) | Blocking length (m) | Single hole dose (kg) | Unit consumption (kg/m 3 ) |
220 | 12 | 14～14.5 | 90 | 7 | 4 | 5 | 5 | 280-320 | 0.8 to 1 |
(1) Hole-by-hole detonation time and detonation network
1, the selection of the time difference
In order to improve the blasting effect and reduce the blasting vibration, a micro-blasting is performed between the blastholes. The detonation sequence and delay time of each blasthole are determined by calculation and combined with the nominal time of each segment of the non-electric detonator.
In order to improve the crushing effect, the time between the holes is mainly the delay time of the detonator in the hole and the minute interval of the detonator outside the hole. The delay time of the detonator in the hole should ensure that the detonator can be detonated when the detonator is far away from the hole. Therefore, the detonator with high delay section is selected in the hole, and the detonator with low section is selected outside the hole.
According to practical experience, the inter-hole differential time is calculated according to the hole spacing of 3 to 8 ms per meter. The hole spacing is 7 m, then the t hole = (3 ~ 8) × 7 = 21 - 56 ms. Three types of detonators of 17, 25, and 42 ms were selected. The row difference time t is calculated by 8 to 15 ms per meter row, then t row = (8 ~ 15) × (4 ~ 5) = 32 ~ 75 ms. A total of 42, 65, 100ms three types of detonators were selected. Since the Taihe vanadium iron ore is generally blasted within 40 holes each time, the 16-segment 400-ms non-electric detonator can be used to meet the demand. In the actual work, 17~42, 25~65, 42~100, 25~42ms are used for pairing. For the explosive type, the matching effect is similar, but for the easy to produce large block, use 17~42 The effect is better when the two modes are 25 to 42 ms.
2, detonation network
The mine has designed and applied three different schemes. After practice verification, it mainly adopts oblique line detonation and V-shaped detonation. Taking 25ms between holes and 42ms between rows as an example, the design parameters of each scheme are shown in Figure 1~3 and Table. 2 to Table 4.
Table 2 Detonation sequence of square cloth holes
Hole number | first row | second row | Third row | Hole number | first row | second row | Third row |
1 2 3 4 | 400 425 450 475 | 442 467 492 517 | 484 509 534 559 | 5 6 7 | 500 525 550 | 542 567 592 | 584 609 634 |
Table 3 Detonation sequence of triangular cloth holes and oblique lines detonation Unit: ms
Hole number | first row | second row | Third row | Hole number | first row | second row | Third row |
1 2 3 4 | 400 425 450 475 | 467 492 517 542 | 509 534 559 584 | 5 6 7 | 500 525 550 | 567 592 | 609 634 659 |
Table 4 Detonation sequence of the V-shaped detonation of the triangular cloth hole Unit: ms
Hole number | first row | second row | Third row | Hole number | first row | second row | Third row |
Left 3 Left 2 Left 1 Explosion hole | 467 442 417 400 | 509 484 459 | 576 551 526 | Right 1 Right 2 Right 3 Right 4 | 425 450 475 | 467 492 517 | 509 534 559 601 |
The three kinds of detonation schemes can realize the detonation by the hole. However, in practice, it is found that the square cloth hole scheme 1 has the largest number, the column and column mineral rock extrusion is not sufficient; the triangle cloth hole and the oblique line detonation scheme II The effect is better than the scheme; the triangular cloth hole V-type initiation scheme is the three-optimal, the explosion pile is fully squeezed, the large block is few, loose and uniform, and it is easy to excavate and transport.
3. Charge structure in the hole
In order to reduce the upper bulk, two types of in-hole charge structures have been adopted (see Figure 4):
(1) Continuous columnar charge, separated by air spacers at the upper blockage;
The blasting effect of the two charging structures is not much different, but the blasting equipment with segmented charging consumes a large amount.
Third, the conclusion
After the use of hole differential blasting technology in Taihe owing mine, the blasting effect is obviously improved. This is mainly reflected in the following aspects:
(1) The blasting block is uniform, the block rate is low, the upper block rate is reduced by 80%, the secondary blasting amount is small, and the base is small;
(2) Controlling the direction of the explosion, reducing the loss of ore and depletion;
(3) It can better control the shape of the explosive pile, improve the looseness and uniformity of the pile, facilitate excavation and transportation, and give full play to the efficiency of the shovel loading and transportation equipment;
(4) Reduced blasting vibration and noise, and less flying stones.
The accuracy of the detonator delay time is the necessary guarantee for the successful realization of the hole-by-hole detonation. The delay is not accurate, which is easy to cause the detonation time to be disordered, and the blasting effect should not be achieved, and the rock throwing direction will be disordered after the detonation. Taihe Iron Mine uses Orica's high-precision non-electric detonators to meet the actual needs of the mine.
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