Open-pit mine perforation blasting technology and blasting measures for adjacent slopes
Piercing is the primary process of open-pit mining. During the entire open-pit mining process, the perforation cost accounts for about 10%-15% of its total production cost.
1. Down-the-hole drill The down-the-hole drill has a wide range of drilling angles and a high degree of mechanization, which reduces the auxiliary operation time and improves the operation rate of the drill. In addition, the down-the-hole drill is flexible and maneuverable, light in weight, and has low investment costs. In particular, it can control the ore grade by drilling various inclined holes, eliminate the foundation, reduce large pieces, and improve the blasting quality. Therefore, down-the-hole drills are currently widely used in small and medium-sized mines at home and abroad, and are suitable for perforating medium-hard ore rocks.
2. Cone drill The cone drill is a modern new type of drilling equipment developed on the basis of the rotary drill. It has the characteristics of high perforation efficiency, low operating cost, high degree of mechanization and automation, and is suitable for perforating ore rocks of various hardness. At present, it has become a perforation equipment commonly used in open-pit mines around the world.
3. Rock Drilling Trolley Rock drilling trolley is a new type of rock drilling equipment that has emerged with the development of the mining industry. It is to install one or several rock drills together with automatic propellers on a special drill arm or stand, and has a walking mechanism to mechanize the operation of the rock drill.
02 Blasting work
The purpose of blasting work is to break hard solid ore and rock, and provide excavated materials with suitable block size for mining and loading work. In the total cost of open-pit mining, blasting costs account for about 15%-20%. The quality of blasting not only directly affects the efficiency of equipment such as mining, transportation, and coarse crushing, but also affects the total cost of the mine.
1. Shallow hole blasting The diameter of the blasthole used in shallow hole blasting is relatively small, generally about 30-75 mm, and the depth of the blasthole is generally less than 5 meters, sometimes up to about 8 meters. If a rock drilling trolley is used to drill a hole, the hole depth can be increased. Shallow hole blasting is mainly used for small-scale open-pit mines or quarries, caverns, tunnel excavation, secondary blasting, new open-pit mine bag processing, the formation of open-pit single-wall ditch transportation channels on hillsides, and some other special blasting.
2. Deep hole blasting Deep hole blasting is a method of blasting the charging space of mining explosives by drilling deeper holes with drilling equipment. The deep hole blasting of open-pit mines is mainly based on the production blasting of steps. The drilling equipment for deep hole blasting mainly uses down-the-hole drills and cone drills. The drilling holes can be drilled vertically or inclined blastholes. The charging of inclined blastholes is more uniform, and the blasting quality of the ore and rock is better, creating good conditions for mining and loading. In order to reduce the seismic effect and improve the blasting quality, under certain conditions, measures such as large-area micro-difference blasting, interval charging in the blasthole or air interval charging at the bottom can be adopted to reduce the blasting cost and achieve better economic benefits.
3. Chamber blasting Chamber blasting is a method of blasting by placing more or a large amount of explosives in the blasting chamber tunnel. Open-pit mines are only used during the capital construction period and under specific conditions, and quarries use it when conditions permit and the demand for mining is large. 4. 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 normal mining and blasting of open-pit mines requires more and more blasting volume each time. For this reason, large-scale blasting methods such as multi-row hole micro-difference blasting and multi-row hole micro-difference extrusion blasting are widely used in open-pit mining at home and abroad. 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%.
5. Multi-row hole micro-difference extrusion blasting method 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 extend 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%-50% larger than that of ordinary micro-difference blasting. 50-100ms is often used in open-pit mines in my country. Compared with multi-row hole micro-difference blasting, the advantages of multi-row hole micro-difference extrusion blasting are: (1) Better ore and rock crushing effect. 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 does not need to be dismantled before blasting, thereby improving the efficiency of mining and transportation equipment. The disadvantages of multi-row hole micro-difference extrusion blasting are: (1) Large consumption of explosives; (2) The working platform requires a wider width to accommodate the slag pile; (3) The height of the blast pile is relatively large, which may affect the safety of excavator operation. 03 Blasting measures near the slope As the open-pit mine extends downward, the stability of the slope becomes increasingly prominent. In order to protect the slope, the blasting near the slope must be strictly controlled. According to domestic and foreign experience, the main measures are to use micro-difference blasting, pre-splitting blasting and smooth blasting. 1. Use micro-difference blasting to reduce vibration. One of the main functions of micro-difference blasting is to reduce the seismic effect of blasting. In order to give full play to the shock-absorbing effect of micro-difference blasting, the key is to try to increase the number of blasting sections and control the micro-difference interval time. 2. Use pre-splitting blasting to isolate the slope. Pre-splitting blasting near the slope is to drill a row of dense parallel boreholes along the boundary of the slope, each hole is loaded with a small amount of explosives, and detonated before the mining zone is blasted, so as to obtain a crack with a certain width and running through each borehole. Because this pre-crack separates the mining zone and the slope, the seismic waves of the subsequent mining blasting will produce a strong reflection on the crack surface, which greatly weakens the seismic waves passing through it, thereby protecting the slope. 3. Use smooth blasting to protect the slope. Smooth blasting near the slope is to drill a row of dense parallel boreholes along the boundary line, load a small amount of explosives in the holes, and blast after the mining borehole blasting, so as to form parallel rock walls along the dense boreholes. The main difference between smooth blasting and pre-splitting blasting is the detonation time. The detonation of smooth blastholes is later than that of the first few rows of mining holes, usually lags by 50 to 75ms. In addition, there is another measure, which is to control the blasting of the last few rows of holes. The amount of explosives and resistance lines of the last few rows of holes near the slope should be reduced, which is called "buffer blasting", which can reduce the damage of drilling and blasting to the slope.
