- 1 Summary of mine blasting methods by Amanda Lee
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Summary of mine blasting methods by Amanda Lee
CLICK HERE NOW TO DOWNLOAD MOST IMPORTANT BOOKS IN CEMENT INDUSTRY + PRACTICAL EXCEL SHEETS TO HELP YOU IN YOUR DAILY WORK
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. This article gives a detailed analysis of the advantages and disadvantages of these blasting methods, and I hope to help everyone.
1. Classification of blasting methods
According to the blasting delay time classification: Qi 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.
2. common blasting methods
1).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.
Applicability of shallow hole blasting: Shallow hole blasting is mainly used for the production of open-pit mines or quarries, meteorites, tunnel excavation, secondary blasting, new open pit mine treatment, and hillside open-air single-ditch transportation. Formation and other special blasting.
2).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.
Characteristics of deep hole blasting: The number of rock blasts in one blasting is large, generally 200,000-1 million tons.
Deep hole blasting can use advanced blasting technology. For example, blasting, blasting and blasting with special requirements can be used for throwing 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.
Application of deep hole blasting: 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 of deep hole blasting: deep holes have vertical deep holes and inclined deep holes. Vertical deep holes are mostly pierced by impact piercers. Most of the inclined deep holes are worn by roller rigs or down-the-hole rigs. For 75 ° – 80 °.
Chamber blasting is the placing of explosives in a pre-cut diverticulum and centralized charging. There are no rules for the amount of explosives that are 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.
Applicability of diverticulum blasting: 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 of chamber blasting:
(1) The preparatory workload is small, and a large number of rock blasting work can be completed in a short time.
(2) Applicable to rocks of various hardnesses, especially in places with complex terrain, which are not subject to construction conditions.
(3) No special rock drilling equipment is required, and the drilling chamber can be used for excavation.
(4) There is no special requirement for the explosives used. Any explosives used for deep hole blasting can be used in chamber blasting.
Disadvantages of chamber blasting: Drilling operators have poor rock drilling conditions and large blasting.
4).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) The amount of blasting is large, the number of blasting and the time of refuge are reduced, and the utilization rate of the stope equipment is improved.
(2) Improve the quality of ore crushing, and its bulk rate is 40%-50% less than single row hole blasting.
(3) The efficiency of the perforating equipment is increased by about 10%-15%, which is due to the increase of 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%-15%.
5).Multi-row hole differential extrusion blasting method
Multi-row hole differential blasting blasting refers to the multi-row hole differential blasting in the case where the working surface has a blasting pile. The existence of piles creates conditions for extrusion. On the one hand, it can prolong the effective action time of blasting and improve the utilization and crushing effect of explosives. On the other hand, it can control the width of the pile and avoid the scattering of 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, the advantages of multi-row hole differential blasting:
(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.
Compared with multi-row hole differential blasting, the disadvantages of multi-row hole differential blasting are:
(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.