Open pit mining is the extraction of useful minerals from open mining sites. Mechanical mining: mining hard ore, deep hole blasting, mechanical mining is the main means of obtaining ore. Manual mining: Announced [2010] No. 17 Civilization Order is banned. Open pit mining simulation 1. Closed circle and open pit mine classification Closed circle: The plane closed curve of the surface of the open pit mining site. According to the topographical conditions buried in the deposit, according to the surface closed circle of open-pit mining, it can be divided into hillside open pit mine and hollow open pit mine. Hillside open pit mine----surface closed circle; The open pit mine is below the surface closed circle. Schematic diagram of hillside open pit mine and sag open pit mine A——Slope open pit mine, B——Sag open pit mine, 1——Elevation of surface closed circle 2. Three elements of open pit mine Step: The rock is divided into horizontal stratification of a certain thickness, and the working level in the mining process forms a stepped shape in space. Each step is called a step and its height becomes the step height. Step slope: The slope faces the side of the gob. The angle between the inclined surface and the horizontal plane is called the step slope angle. Platform (flat): The space on the horizontal plane between the bottom line of the step and the top line of the slope. The width between the bottom line and the top line is called the platform width. The platform in the blasting, shovel loading and transportation operations is called the working platform; the width between the blasting edge and the top line is called the working platform height; The platform that blocks the falling rocks is called a safe (cleaning) platform. 3. Mining technology of open pit mines The mining technology of open pit mines is relatively simple, mainly including perforation, blasting, mining and transportation, and rock discharge. Next, we will talk specifically about the mining process of open pit mines. First, the piercing work Perforation is the primary process in open pit mining. During the entire open pit mining process, the cost of perforation accounts for about 10%-15% of the total cost of production. 1. DTH drilling rig The downhole drilling rig has a wide range of drilling angles, high degree of mechanization, reduced auxiliary working time, improved drilling rig operating rate, and the downhole drilling rig is flexible, light in weight, low in investment cost, especially through drilling various kinds of drilling rigs. Oblique holes to control the ore grade can eliminate roots, reduce large blocks, and improve the quality of blasting. Therefore, the down-the-hole drilling rig is widely used in small and medium-sized mines at home and abroad, and is suitable for perforation of medium-hard rock. 2, roller rig The roller rig is a modern new drilling equipment developed on the basis of rotary drilling rig. It has the characteristics of high perforation efficiency, low operating cost, mechanization and high degree of automation. It is suitable for perforation of rock with various hardness. Currently, It has become a perforated device commonly used in open pit mines all over the world. 3. Rock drilling rig Rock drilling rigs are a new type of rock drilling equipment that has emerged along with the development of the mining industry. It is to install one or several rock drills together with the automatic propeller on a special drill arm or gantry, and has a running mechanism to mechanize the rock drill operation. Second, the blasting work The purpose of the blasting work is to break up hard solid ore and provide a suitable piece of excavation for the loading work. Among the total cost of open pit mining, the blasting costs account for about 15%-20%. The quality of the 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 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. 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. . 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. Drilling equipment for deep hole blasting mainly uses downhole drilling and roller drilling. The drill hole can drill vertical deep holes or drill the inclined blast holes. The charge of the inclined blasthole is relatively uniform, and the blasting quality of the rock is good, which creates favorable conditions for the loading and unloading work. In order to reduce the seismic effect and improve the blasting quality, under certain conditions, large-area milli-blasting, interval charge in the blasthole or bottom air-spaced charge can be taken to reduce the blasting cost and achieve better economic benefits. 3, chamber blasting Chamber blasting is a method of blasting a large or large amount of explosives in a tunnel of a blasting chamber. 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. 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. For this reason, multi-row holes are widely used in open pit mining at home and abroad. Large-scale blasting methods such as millisecond blasting, multi-row hole differential blasting and blasting. Advantages of multi-row hole differential blasting: A large amount of blasting, reducing the number of blasting and avoiding time, and improving the utilization rate of the stope equipment Improve the quality of ore rock breakage, its bulk rate is 40%-50% less than single row hole blasting Improve the efficiency of the perforating equipment by about 10%-15%, which is due to the increase of the working time utilization factor and the decrease in the number of punching equipment and the number of filling operations after blasting Improve the efficiency of mining and transportation equipment by about 10%-15%. 5, multi-row hole differential extrusion blasting method Refers to the multi-row hole differential blasting in the case where the working surface has a blasting pile. 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. The advantages of multi-row hole differential blasting are: (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 the use of railway transport mine, may not be removed before blasting channel, thereby improving the mining equipment, transportation equipment efficiency. The disadvantages of multi-row hole differential blasting are: Explosives are consumed in large quantities; The working platform is required to be wider to accommodate the stack; The height of the explosion pile is large and may affect the safety of the excavator. Third, the blasting measures adjacent to the slope As open pits deepen downward, the problem of slope stability has become increasingly prominent. In order to protect the slope, the blasting of the adjacent slope should be strictly controlled. According to domestic and international experience, the main measures are the use of millisecond blasting, pre-crack blasting and smooth blasting. 1, using millisecond blasting to reduce vibration One of the main effects of millisecond blasting is to reduce the seismic effects of blasting. In order to give full play to the shock absorption effect of millisecond blasting, the key is to increase the number of blasting segments and control the interval between the differentials. 2. Separating the slope by pre-split blasting Pre-splitting blasting near the slope is to drill a row of dense parallel boreholes along the boundary of the slope, each hole is filled with a small amount of explosives, and the mining belt is detonated before it is blasted, thereby obtaining a certain width and running through the holes. Crack. Since the pre-crack separates the mining belt from the slope, the seismic wave of the subsequent blasting will produce a strong reflection on the crack surface, so that the seismic wave passing through it is greatly weakened, thereby protecting the slope. 3, using smooth blasting to protect the slope The smooth blasting of the adjacent slope is to drill a row of dense parallel boreholes along the boundary line. A small amount of explosives is placed in the holes, and then blasting is performed after the mining boreholes are blasted to form parallel rock walls along the dense boreholes. The difference between the smooth blasting and the pre-cracking blasting is mainly at the detonation time. The detonation of the smooth blasthole is later than the first few rows of mining boreholes, usually lags 50 to 75 ms. In addition to this, there is a measure to control the blasting of the last few rows of holes. The dose and resistance line of the last row of drills near the slope are reduced, which is called “buffer blastingâ€, which can reduce the damage of the blasting to the slope. Fourth, mining and transportation The loading operation is to use the loading machinery to excavate the ore directly from the underground or the explosion, and load it into the compartment of the transportation machinery or directly to the designated place. It is the central link of the open-pit mining process, and other production processes such as wearing and blasting, transportation, etc. are all for the purpose of loading and unloading. Main equipment: excavators, bucket shovel, hydraulic shovel and tire front loading machine. In the open-pit mining process, the capital construction investment of mine transportation accounts for about 60% of the total investment in mine infrastructure. The transportation cost and labor volume account for more than half of the total ore cost and total labor, respectively. The important position in the. Open-pit mine transportation modes: automobile transportation, railway transportation, tape transportation, slope bucket lifting transportation and joint transportation mode, of which dump truck transportation is the most common. The installation and transportation are inseparable, and the two influence each other and restrict each other. At present, the development trend of the loading and transportation process is mainly reflected in the large-scale production and transportation equipment, the integration and continuity of the loading and transportation links, and computer automation. Five, row of rock The bouldering is the operation of the transportation terminal, and the topsoil and waste rock under the stripping are transported to the waste rock yard for disposal. Drilling technology: railway transportation, rock discharge, road transport, rock transport, belt transport, rock discharge Sixth, dumping site Dumping site (waste yard): The place where the stripping material is piled up refers to the place where the mining waste is concentrated and discharged. According to the stacking sequence, the dumping site can be divided into a single-step dumping site, a covered multi-step dumping site, and a multi-step dumping site with a pressure-slope foot. According to the dumping process, the dumping site is mainly divided into: road transport dumping site, railway transport dumping site, tape transport dumping site and hydraulic transport dumping site. 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