First, the perforation operation and safety requirements
1. Basic situation of perforation operation
Perforation is the first step in open pit mining, and the purpose is to provide holes for explosives to be placed in the blasting work. The quality of the perforation is directly related to the efficiency of subsequent work such as blasting, loading and crushing.
Perforation methods: two methods of thermal fracture perforation and mechanical fracture perforation.
Perforation equipment: Common perforated rock drilling equipment is divided into shallow hole rock drills ( rock drills and rock drilling rigs) and deep hole rock drills (cone drilling and downhole drilling rigs ) according to the piercing depth.
2. Technical performance of rock drill
(1) roller rig
The roller rig is a highly efficient perforating device widely used in large open pit mines in China. According to the perforation size, the speed of perforation of the roller rig is generally 4000~6000m/month, and the highest can reach 10000m/month; if it is calculated according to the annual wear volume, it is generally 4 million to 6 million tons, up to 12 million. 14 million tons, 4 to 5 times that of wire rope impact drills. The drilling speed of the roller rig is about 40% to 100% higher than that of the downhole drilling rig.
From the economic effect, the cost of perforation of the roller rig is also the lowest, about 75% of the wire rope impact drill, and 70% of the downhole drilling rig.
Disadvantages: The roller rig is heavy and expensive, about 2 million/set, and the drill bit is 20,000-30,000, accounting for 40%-50% of the drilling cost. It can reduce the drilling by improving the quality of the drill bit and prolonging its service life. cost.
(2) DTH drilling rig
The down-the-hole drilling rig is a kind of perforating equipment that was used in China in the 1950s. In the 1960s, it replaced the wire rope impact drill, which is mainly suitable for small and medium-sized open pit mines.
Its main features are:
1The hole diameter is small (Φ150~200mm), the inclined hole can be drilled, and the blasted ore rock is small, which is convenient for the use of small excavators.
2 The device has simple structure, convenient operation and maintenance, flexible maneuverability and low price.
3 The efficiency of the equipment is better, the drilling efficiency is 2000m/(tai.month), and the amount of rock in the Taiwanese period is about 600,000~1.5 million tons.
(3) Rock drilling rig
The drilling rig is a perforating device using a rail type heavy-duty pneumatic rock drill. Due to its simple and flexible equipment and small aperture, it can be used to punch blastholes at any angle. It has obvious effects on improving labor productivity and improving working conditions, and is widely used in small mines.
3. Rock drilling safety requirements
Second, blasting operations and safety requirements
Blasting operations are an important process in open pit mining, providing suitable ore deposits for subsequent loading, transportation, and crushing. Therefore, the quality of the blasting process has a great impact on the follow-up work.
1. Blasting method
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.
(1) Shallow hole blasting method
The shallow hole blasting method has a small bore diameter (generally 28-75 mm), and the hole depth is generally 5-8 m. Due to the limitation of the aperture and the depth of the hole, the amount of blasting is small and cannot meet the requirements of large-scale shipping equipment. Therefore, this blasting method is mainly used in small open pit mines or in the case of complicated geological conditions and special requirements for the geometry of the blasted ore. Large and medium-sized open-pit mines use this blasting method to perform secondary blasting to treat the orphans suspended in the root or working surface.
(2) Deep hole blasting method
Deep hole blasting is the most widely used blasting method 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. 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.
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.
Whether the deep hole blasting can be carried out smoothly and the blasting effect is good or bad is closely related to the preparation work before blasting. Therefore, preparations must be made before the deep hole blasting.
(3) 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.
2. Open pit mining and blasting
Due to the continuous development and renewal of open pit mining machinery , the mine productivity has been greatly improved. Therefore, it is necessary to adopt a blasting method with a large amount of blasting to meet 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. A 500,000 t.
Multi-row hole differential blasting: 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).
Multi-row hole differential blasting blasting: Multi-row hole differential blasting blasting refers to multi-row hole differential blasting under the condition that there is residual pile in the working surface.
The common detonation sequence for multi-row hole differential blasting is as follows:
1 single row hole blasting detonation sequence
The millisecond blasting of a single row of holes mostly adopts the order of detonation between the holes. This method is simple and easy to grasp. This method is mostly used in the mining and blasting operation of the step working face. The detonation sequence is shown in Figure 4-10.
Detonation sequence of 2 blast row fine blasting
This method is also relatively simple, and in general, the effect is better. The blasthole arrangement of the differential blasting of multi-row rows is mostly triangular. Sometimes arranged as a square, the detonation sequence is shown in Figure 4-11.
3 detonation sequence of wavy differential blasting
This detonation sequence has the characteristics of the above two types of millisecond blasting, the rock pulverization is good, the blasting width is small, and the blasthole arrangement is complicated, and most of them are used for working surfaces where the ore is difficult to blast or is prone to large blocks. However, the connection sequence of this detonation is more complicated and easy to leave. The detonation sequence is shown in Figure 4-12.
4 diagonal differential blasting initiation sequence
This detonation sequence ensures a minimum detonation pile width and a small rock mass scattering distance. The detonation sequence is shown in Figure 4-13.
5 wedge differential blasting initiation sequence
Wedge-shaped detonation, the number of rows in the blasthole is more, such as the use of roller shovel. The rock is crushed better because of its squeezing and impacting action. The wedge-shaped initiation sequence is shown in Figure 4-14.
According to the practical experience of multi-row hole differential blasting in domestic mines, the following matters should be noted when implementing multi-row hole differential blasting:
(1) The influence of the thickness of the slag pile on the width of the pile. In order to protect the circuit of the step working surface, the requirements of Table 4-4 must be referred to when charging.
(2) Unit explosive consumption and dosage distribution. The consumption of unit explosives in multi-row hole differential blasting is about 20% to 30% larger than that of ordinary differential blasting.
(3) Differential interval time. Since the blasting is to push the slag pile in front, the interval between detonation is generally 50-100 ms.
(4) The number of blasting rows and the order of detonation. The number of rows of extrusion blasting is generally more than four rows. In addition to the several detonation sequences of ordinary millisecond blasting, there is also a ring initiation sequence, as shown in Figure 4-15.
3. Blasting safety and methods
(1) Open pit mine blasting safety
Main blasting hazard factors of open pit mine: blasting vibration, air shock wave, blasting flying stone, harmful gas, blasting noise.
Preventive measures for open pit mine blasting: differential blasting, extrusion blasting, control of single-stage detonation dose, reasonable determination of blasting safety distance, alarm signal, setting of boundary and warning points.
(2) Open pit mine production blasting procedures
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