We know that open pit Mining operations mainly include perforation, blasting, mining, transportation and dumping. Blasting is a very important part of it, and the blasting costs account for 15-20% of the total cost of open pit mining. Moreover, the quality of the blasting directly affects the efficiency of equipment such as mining, transportation, coarse crushing and the total cost of the mine. Today, Xiaobian will share several common blasting methods in open pit mining and their application.
Blasting method classification
In open pit mining, the commonly used blasting methods are as follows:
According to the blasting delay time classification: uniform blasting, second blasting, and millisecond blasting.
Classified by blasting method: shallow hole blasting, medium deep hole blasting, chamber blasting, multi-row hole differential blasting, multi-row hole differential blasting blasting, medicine pot blasting, external blasting, hole-by-hole blasting technology.
5 common blasting methods
Shallow hole blasting
The diameter of the blasthole used in shallow hole blasting is small, generally about 30~75 mm. The depth of the blasthole is generally less than 5 meters, sometimes up to 8 meters. If drilling with a rock drilling rig, the hole depth can be increased.
Applicable conditions:
Shallow hole blasting is mainly used to produce open-pit mines or quarries, vermiculite, tunnel excavation, secondary blasting, new open pit mine treatment, formation of hillside open-air single-wall ditch transportation and other special blasting. .
Deep hole blasting
Deep hole blasting is the use of drilling equipment to drill deep boreholes as a blasting method for the charging space of mining explosives. Deep hole blasting in open pit mines is mainly based on production blasting of steps. Deep hole blasting is a blasting method widely used in open pit mines. The depth of the blasthole is generally 15-20m. The aperture is 75~310mm, and the commonly used aperture is 200~250mm.
Features:
The number of rock ore that is blasted once is large, generally 200,000 to 1 million tons;
Deep hole blasting can use advanced blasting technology. Such as millisecond blasting, squeezing blasting and explosion areas with special requirements can be thrown blasting and directional blasting;
The blasting operation is relatively safe and the management is relatively simple. There is no special requirement for the explosives except for the deep holes with water, and the detonation method is also flexible.
Applicable conditions:
Deep hole blasting is widely used in the production of ditching, stripping and mining of large mines. Its blasting capacity accounts for more than 90% of the total blasting capacity of large mines.
classification:
Deep holes have vertical deep holes and inclined deep holes. Vertical deep holes are mostly worn by impact piercers. Most of the inclined deep holes are worn by the roller rig or the downhole drilling rig. The inclination is generally 75 to 80 degrees.
Chamber blasting
Chamber blasting is to place the explosive in a pre-cut diverticulum and concentrate the charge. There is no rule for the amount of explosives that can be detonated each time, and some are loaded with tens of tons, hundreds of tons or thousands of tons. Because of the large amount of blasting, it is also called large blasting.
Applicable conditions:
Open pit mines are only used during basic construction periods and under specific conditions, and quarries are used when conditions are met and when mining demand is high.
Advantages and disadvantages:
advantage
1, the preparation workload is small, and a large number of rock blasting work can be completed in a short time;
2, suitable for rock of various hardness, especially in places with complex terrain, not subject to construction conditions;
3, no special rock drilling equipment is required, and the drilling chamber can be used for excavation by using a rock drill;
4. There is no special requirement for the explosives used. Any explosives used in deep hole blasting can be used in chamber blasting.
Disadvantage
The excavation operator has poor rock drilling conditions and a large number of blasting.
Multi-row hole differential blasting method
In recent years, with the sharp increase in the capacity of excavator buckets and the production capacity of open pit mines, the amount of blasting required for normal mining blasting in open pit mines is increasing. Therefore, it is necessary to use a blasting method with a large amount of blasting. Adapt to the needs of new mining machinery. At present, the blasting method with a large amount of blasting in China is to use multi-row hole differential blasting and multi-row hole differential blasting blasting method. These two methods can blast 5~10 rows of blastholes at one time, and the amount of blasting ore can reach 300,000. ~500,000 tons.
Millisecond blasting is a blasting method in which the adjacent blastholes are sequentially detonated in a pre-designed order within a very short time (calculated in ms).
Advantages of multi-row hole differential blasting:
(1) A large amount of blasting, reducing the number of blasting and avoiding time, and improving the utilization rate of the stope equipment;
(2) Improve the quality of ore crushing, and its bulk rate is 40%~50% less than that of single row hole blasting;
(3) Increasing the efficiency of the perforating equipment by about 10% to 15%, which is due to the increase in the utilization factor of the working time and the decrease in the number of operations of the perforating equipment and the filling area after the blasting;
(4) Improve the efficiency of mining and transportation equipment by about 10% to 15%.
Multi-row hole differential extrusion blasting method
Multi-row hole differential blasting blasting refers to multi-row hole differential blasting under the condition that there is residual blasting on the working surface. The existence of the pile creates conditions for the extrusion. On the one hand, it can prolong the effective action time of the blasting, improve the utilization and crushing effect of the explosive energy; on the other hand, it can control the width of the explosion and avoid the scattering of the ore. The differential interval of multi-row hole differential squeezing blasting is 30%~50% larger than that of ordinary millisecond blasting. China's open pit mine often uses 50~100ms.
Compared with multi-row hole differential blasting, multi-row hole differential blasting:
The advantage is:
(1) The rock crushing effect is better. This is mainly due to the slag heap blocking in front, and the rows of drill holes including the first row can increase the amount of charge and fully break under the slag pile extrusion;
(2) The explosion pile is more concentrated. For mines that are transported by rail, they may not be dismantled before blasting, thereby improving the efficiency of the loading and transportation equipment.
weakness is:
(1) The consumption of explosives is large;
(2) The working platform is required to be wider to accommodate the stack;
(3) The height of the explosion pile is large, which may affect the safety of the excavator operation.
In addition, no matter what kind of blasting method is used, the blasting safety regulations must be strictly implemented during the blasting operation, safety warning signs should be set, and the warning work should be done to ensure the safety of personnel and property.
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