5 blasting methods, there is always one method suitable for your mine!
New technology: O2 rock demolition system
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Open-pit mining operations mainly include drilling, blasting, mining, transportation and soil discharge. Blasting is a very important part of it, and blasting costs account for 15-20% of the total cost of open-pit mining. Moreover, the quality of blasting directly affects the efficiency of equipment such as mining, transportation, and coarse crushing and the total cost of the mine.
Classification of blasting methods
In open-pit mining, the commonly used blasting methods are as follows:
Classification by blasting delay time: simultaneous blasting, second difference blasting, and micro-difference blasting.
Classification by blasting method: shallow hole blasting, medium and deep hole blasting, chamber blasting, multi-row hole micro-difference blasting, multi-row hole micro-difference extrusion blasting, medicine pot blasting, external application blasting, hole-by-hole detonation technology.
5 Common Blasting Methods
01 Shallow Hole Blasting
The diameter of the blast-hole used in shallow hole blasting is relatively small, generally about 30~75 mm, and the depth of the blast-hole is generally less than 5 meters, sometimes up to about 8 meters. If the hole is drilled with a rock drilling trolley, the hole depth can be increased.
Applicable situations:
Shallow hole blasting is mainly used for open-pit mines or quarries with small production scale, cave stones, tunnel excavation, secondary blasting, new open-pit mine mountain bag processing, the formation of open-pit single-wall ditch transportation channels on hillsides, and some other special blasting.
02 Deep hole blasting
Deep hole blasting is a blasting method that uses drilling equipment to drill deeper holes as the charging space for mining explosives. Deep hole blasting in open-pit mines is mainly based on production blasting of steps. Deep hole blasting is a widely used blasting method in open-pit mines. The depth of the blast-hole is generally 15~20m. The hole diameter is 75~310mm, and the commonly used hole diameter is 200~250mm.
Features:
The amount of rock and ore blasted at one time is large, generally 200,000 to 1 million tons;
Advanced blasting technology can be used for deep hole blasting. For example, micro-difference blasting, extrusion blasting, and blasting areas with special requirements can use throwing blasting and directional blasting;
The blasting operation is relatively safe and simple to manage. There are no special requirements for explosives except for deep holes with water, and the detonation method is also relatively flexible.
Applicable situations:
Deep hole blasting is widely used in the production links of trenching, stripping, mining, etc. in large mines. Its blasting volume accounts for more than 90% of the total blasting volume of large mines.
Classification:
Deep holes are divided into vertical deep holes and inclined deep holes. Vertical deep holes are mostly drilled by impact perforators. Inclined deep holes are mostly drilled by rotary drills or down-the-hole drills. The inclination is generally 75° to 80°.
03 Chamber blasting
Chamber blasting is to place explosives in a pre-drilled chamber and load them centrally. There is no rule for the amount of explosives used in each detonation, and some are loaded with dozens, hundreds or thousands of tons. Because the amount of explosives blasted at one time is large, it is also called large blasting.
Applicable situations:
Open-pit mines are only used during the capital construction period and under specific conditions, and quarries are used when conditions permit and the demand for mining is large.
Advantages:
1. Less preparation work, a large amount of rock blasting can be completed in a short time;
2. Applicable to rocks of various hardness, especially in places with complex terrain, which are not restricted by construction conditions;
3. No special rock drilling equipment is required, and the excavation chamber can generally be excavated using a rock drill;
4. There are no special requirements for the explosives used, and all explosives used for deep hole blasting can be used in chamber blasting.
Disadvantages:
The excavation operator has poor rock drilling conditions and blasts more large pieces.
04 Multi-row hole micro-difference blasting method
In recent years, with the rapid increase in excavator bucket capacity and open-pit mine production capacity, the amount of blasting required for normal open-pit mining blasting is also increasing. Therefore, a blasting method with a larger blasting volume must be adopted to meet the needs of new excavation machinery. At present, the blasting methods with a larger blasting volume in one blasting volume in my country are multi-row hole micro-difference blasting and multi-row hole micro-difference extrusion blasting. These two methods can blast 5 to 10 rows of blast holes at a time, and the blasting volume of ore and rock can reach 300,000 to 500,000 tons.
Micro-difference blasting refers to a blasting method in which the explosive bags in adjacent blast holes are detonated in sequence in a very short time (calculated in ms) according to a pre-designed order.
Advantages of multi-row hole micro-difference blasting:
(1) A large amount of blasting is produced at one time, which reduces the number of blasting times and the time to avoid blasting, and improves the utilization rate of mining equipment;
(2) Improves the quality of ore and rock crushing, and its large block rate is 40%~50% less than that of single-row hole blasting;
(3) Improves the efficiency of perforating equipment by about 10%~15%, which is due to the increase in the utilization coefficient of working time and the reduction in the number of operations of perforating equipment and post-blasting filling area;
(4) Improves the efficiency of mining, loading and transportation equipment by about 10%~15%.
05 Multi-row hole micro-difference extrusion blasting method
Multi-row hole micro-difference extrusion blasting refers to multi-row hole micro-difference blasting when there is a blast pile remaining on the working face. The existence of slag pile creates conditions for extrusion. On the one hand, it can prolong the effective action time of blasting, improve the utilization of explosive energy and the crushing effect; on the other hand, it can control the width of the blast pile and avoid the scattering of ore and rock. The micro-difference interval time of multi-row hole micro-difference extrusion blasting is preferably 30% to 50% longer than that of ordinary micro-difference blasting. 50 to 100ms is often used in open-pit mines in my country.
Compared with multi-row hole micro-difference blasting, multi-row hole micro-difference extrusion blasting has the following advantages:
(1) The ore and rock crushing effect is better. This is mainly due to the slag pile blocking in front. Each row of drill holes, including the first row, can increase the charge and fully crush under the pressure of the slag pile;
(2) The blast pile is more concentrated. For mines that use railway transportation, the track can be left untouched before blasting, thereby improving the efficiency of mining and transportation equipment.
Disadvantages:
(1) The consumption of explosives is large;
(2) The working platform is required to be wider to accommodate the slag pile;
(3) The height of the blast pile is large, which may affect the safety of the excavator operation.
In addition, no matter what blasting method is used, the "Blasting Safety Regulations" must be strictly implemented during blasting operations, safety warning signs must be set up, and vigilance work must be done well to ensure the safety of personnel and property.
