(1) Minefield development

Develop content

First, you need to excavate the passage from the ground to the underground. A coal mine there are at least two channels, said a main shaft for coal shipped; one for the auxiliary shaft to transport personnel, equipment, transport equipment and the gangue. There is also a need for a well-ventilated wind shaft. The main and auxiliary shafts are generally built in the same industrial square. If central ventilation is used, the wind wells are close to the main and auxiliary shafts; if diagonal ventilation is used, the wind shafts are built at the boundary of the well fields.

After the wellbore is dug to a predetermined depth, a series of roadways and diverticulum are to be excavated at the elevation and above, including the bottom hole yard, the transportation lane, the Shimen, the uphill and downhill, the return roadway, the communication roadway, and the underground coal. Warehouse, water tank, pump house, substation, pressure fan room, warehouse, etc. This elevation is called the production level. These roadways and diverticulums have been providing services throughout the entire production period of the mine.

The underground coal seam is divided into several areas for mining, and this area is the mining area. According to the production requirements, coal seam thickness, coal mining methods, etc., a mine can be produced in one mining area or in multiple mining areas. A new mine has been developed into a transportation and ventilation network for the entire mine, and a production area that is compatible with the designed output is prepared, which can be transferred to production, which is called production. In order to meet the needs of coal mining in the production mining area, it is necessary to excavate a lot of roadways. These roadways are called production and excavation with coal mining, and are not part of the development of the mine field.

2. Ways of development

Including vertical shaft development, inclined shaft development, development and comprehensive development.

The vertical shaft development has the shortest distance from the ground to the bottom of the well, and most coal mines use it. The vertical shaft depth was 595.8 m in 1990, and there are many vertical shafts in the eastern region with a depth of more than 1,000 meters. The diameter of the wellbore is determined according to the coal production, generally 2 to 8 m. The auxiliary well is also used as the inlet well, and the section is the largest; the main well specializes in upgrading the coal, the wind well is used for the wind, and the section can be small.

According to the characteristics of the strata, especially the characteristics of the topsoil, the wellbore development is divided into ordinary well drilling method and special well drilling method. The ordinary drilling method does not require pre-reinforcement of the formation, and the drilling blasting method is mainly used. After excavating a section of height, the reinforced concrete permanent shaft wall is built. When some water-bearing rock formations are encountered, they should be pre-grouted, and the slurry holes can be drilled in the ground or grouted from the working surface. When the wellbore passes through the sand-sand layer, the ordinary well-drilling method cannot be used, and a special well-drilling method must be used. In eastern China, the use of special well drilling methods is quite common. These include the freezing method, the drilling method, the sinking method and the curtain method.

The freezing method is to freeze the aquifer around the wellbore by artificial refrigeration to form a closed cylindrical freezing wall with a certain thickness, and then excavate the wellbore under the protection of the wall. It includes three steps of freezing holes, freezing and excavation: the freezing holes are used to construct dozens of equidistant holes along the appropriate distance outside the diameter of the wellbore, and the seamless steel pipes of the back cover are sent down to fix, then the strata and The heat exchange at the freezing station takes place through a seamless steel pipe. The ammonia compressor for freezing is completed by continuously circulating brine. The freezing of a few hundred meters of formation into a frozen soil wall requires the construction of a large freezing station, which can be completed in a few months. The freezing work after excavation should continue until the wellbore is completely completed. Wellbore excavation is the same as ordinary construction methods. Generally, wind digging is used. If drilling blasting is required, the amount of explosives should be less to prevent damage to the freezing pipe. The support of the excavation process requires the stress and strain effect of the frozen soil wall during the thawing process. Therefore, when the whole well is dug, a second permanent support is required from the bottom up.

The drilling method is a method of excavating a wellbore with a large diameter rig , including two steps of drilling and suspending the sinking wall. In order to ensure the verticality of the wellbore, the decompression drilling method is adopted, and the drill bit is in a semi-suspended state. Due to the large diameter of the wellbore, a multi-stage drill bit is required, and the required diameter can be achieved after multiple drilling. At the same time of drilling, the reinforced concrete or steel-steel composite composite wall is prefabricated on the ground, joined at the wellhead by section, and the whole suspension is sunk to a predetermined depth, and then the cement slurry is used to fill the space.

The sinking method is to force the reinforced concrete wellbore perfused on the ground to be forced to sink by its own weight or self-weight plus additional force. In order to reduce the sinking resistance, a step and a blade angle slightly larger than the outer diameter are formed at the bottom of the wellbore, and the annular space above the step is supported by the thixotropic mud. This method is technically difficult and requires a uniform texture of the soil layer through which the wellbore passes to avoid deflection.

The curtain method is to build a circle of water and a concrete wall with sufficient strength around the wellbore to form a curtain, and then use the common construction method to excavate and support under the protection. The wall thickness is generally 0.8 to 1 m.

Another type of minefield development method is an inclined well, that is, a wellbore excavated from the ground, including a main inclined shaft, a secondary inclined shaft, and a diagonal well. The angle of the inclined well is generally 15 ° ~ 25 °. The main inclined shaft is used to raise coal, and the ability to lift with the mine car is small, and the belt conveyor has a large lifting capacity. The auxiliary inclined shaft is used for personnel and material transportation, and also serves as an air intake well. Compared with the vertical shaft, the length from the wellhead to the bottom of the well is several times larger, but the excavation cost is low and the method is much simpler.

Pingyi is the easiest way to open up, but it is only suitable for mountainous areas. The coal seam below the development level still needs to be developed from a dark inclined or dark well to a new level.

(ii) Coal mining underground

1. Mining sequence and method

For coal seams with a dip angle of 10° or more, the coal seams are generally mined horizontally. Each level is divided into several mining areas. The coal seams in each mining area are firstly mined in the first level, and then transferred to the next level after the mining. When mining near-horizontal coal seams, the coal seams are first divided into several panels. After the silo reaches the coal seam at the center of the minefield, the panels near the wellbore are firstly taken, and the farther panels are taken. If there are two or more layers of coal seams, the first level of the uppermost coal seam is first taken, and then another coal seam is taken from top to bottom, and transferred to the second level after the harvest.

According to the technology of falling coal, underground coal mining has three types: mechanical coal falling, blasting coal falling, and hydraulic falling coal. The former two are called dry mining, the latter is called water mining, and China's water mining wells only account for 1.57%. Dry mining includes wall mining method and column coal mining method, the former is the main one. The wall type coal mining method has a long working face, generally 100 to 200 m, and can accommodate coal mining machinery with high power and high production capacity, so the output is large and the efficiency is high. The column coal mining method has a short working face, generally 6 to 30 m. Due to the short working face, the roof is easy to maintain, thus reducing the maintenance cost. The main disadvantage is that the recovery rate is low.

2. Production system

These include coal mining systems, tunneling systems, ventilation systems, drainage systems, power supply systems, auxiliary transportation systems, and security systems.

The coal mining system includes coal falling and coal loading on the working face, and the coal is transported from the working face to the bottom hole yard until it is raised to the ground. The main wells include coal mining face, mining area along the trough, mining area uphill, horizontal transportation alley, Shimen and so on. The main equipments include coal mining machines, transportation machinery, support equipment and hoists.

The tunneling system is to ensure the continuous production, that is, at the same time of production, new working faces, mining areas and production levels should be excavated for replacement. It includes the excavation working face, the meteorite transported to the bottom of the well, and the auxiliary shaft is lifted and sent to the stacking ground. The main equipment includes equipment used for excavation, support, transportation, lifting, etc., as well as pneumatic rock drills , air compressors and their pipelines.

The ventilation system consists of an air inlet shaft, a return air shaft, a ventilator and a downhole ventilation facility such as a wind bridge and a damper.

The drainage system consists of a ditch, a water tank, a pump chamber, a water pump and a drain line in the roadway.

The requirements of the power supply system must not be interrupted to ensure safety. Therefore, the supply current is a double circuit. At the same time, the electrical equipment entering the mining area and the return air passage must be mine explosion-proof to prevent gas explosion.

Auxiliary transportation systems include personnel up and down and transportation of materials and equipment.

Safety systems include equipment, facilities, equipment, instrumentation and monitoring systems needed to prevent gas explosions, gas outbursts, and downhole fires and floods.

3. Mining face

The coal mining face is the working place for underground coal mining. As the coal mining progresses, the working face continues to advance, and the original mining site becomes a goaf. The coal mining process in the longwall face is five items: coal breaking, coal loading, coal transportation, support and roof control; the short-wall working face has only the first four processes. The drum type coal mining machine is mainly composed of long-wall working face comprehensive mechanization equipment, which can complete five main processes, called comprehensive mechanized coal mining, referred to as comprehensive mining, which is called fully mechanized mining face.

The excavation working face is the working place of the roadway excavation, which is divided into three types: rock lane, coal lane and semi-coal rock lane. The excavation process is divided into three parts: rock, shipping and support. There are two types of tunneling methods, one is the drilling and blasting method, and the other is the use of the roadheader. The former has a wide range of applications but low degree of mechanization. The latter includes two types of full-face rock tunneling machines and cantilever roadheaders. Coal mines generally use cantilever-type roadheaders, including roadheaders, transfer machines, transporters and support equipment to form a comprehensive mechanization of tunneling, completing three main processes, called comprehensive excavation.

4. Coal mining mechanization classification

According to the geological conditions of China's coal mines and actual production conditions, mechanization is divided into three levels:

Common mechanized mining, referred to as conventional mining, coal mining face with Shearer, flexible chain conveyor and the friction metal pillars, the metal roof beam apparatus, the first three steps can complete mechanization, but less power, generally The annual output of the working face is 15 to 200,000 tons.

High-grade general mechanized coal mining, referred to as high-grade general mining. The coal mining face is equipped with a shearer, a bendable chain conveyor, hydraulic props and metal top beams to mechanize the first three processes. Because of the hydraulic props, the top plate is in good condition. Although the support and the top control are manual operations, the labor intensity is greatly reduced and the power is also large. The annual output is 200,000 to 300,000 tons.

Comprehensive mechanized coal mining, referred to as comprehensive mining. Mechanization of five processes can be completed. Current performance continues to improve, capabilities continue to increase, operations are increasingly simplified, and applications are expanding. The highest record is the working face of the first-class mining team of Wangzhuang Mine of Shanxi Lu'an Mining Bureau, with an annual output of 2.53 million tons.

(3) Open coal mining

Removing the rock and coverings over the coal seam and exposing the coal to the surface is called open-pit mining. The process of removing the soil rock is called stripping, and the process of producing coal is called coal mining. Open-pit coal mining usually divides the well field into several horizontal layers, which are mined from top to bottom and form a stepped shape in space.

Main production link

Firstly, the perforated blasting is used to mechanically disintegrate the rock coal in advance, and then the rock coal is extracted from the whole by the mining equipment, and loaded into the transportation equipment, transported to the designated place, and the stripping material in the transportation equipment is discharged to the yard according to the procedure; Unload coal at a coal washing plant or other unloading point.

2. Main advantages and disadvantages

The advantage is that the production space is not limited, large-scale mechanical equipment can be used, the mine scale is large, the labor efficiency is high, the production cost is low, and the construction speed is fast. In addition, the resource recovery rate can reach more than 90%, the resource utilization is reasonable, and the labor conditions are good, the safety is guaranteed, and the death rate is only about 1/30 of the underground coal mining.

The main disadvantage is that it takes up a lot of land, which will cause certain environmental pollution, and the production process needs to be restricted by topography and climatic conditions. In terms of resources, the requirements for coal storage conditions are strict, and it should only be used in mining areas with shallow burial and large coal seam thickness.

3. Overview of open pit coal mining in China

The earliest open-pit mine in China was Fushun West Open-air, built in 1914. Since the founding of New China, 78 open-pit mines have been built, with a total design scale of 58.85 million t/a, the largest of which is the Antaibao open-pit mine, with a scale of 15.33 million t/a, followed by the Huolin River mine, scale 1 10 million t/a. The large-scale open-pit mine under construction also has the Junggar Black Gully, with a scale of 12 million t/a, Yuanbao Mountain with a scale of 5 million t/a, and Yimin with a scale of 5 million t/a. Open-pit mine production accounts for about 5% of coal annual output, and the proportion is low. With the development of large-scale open-pit mining equipment, the annual output of open-pit mines in 2000 is expected to reach 100 million tons.

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