1. Features of mining method for steep coal seams
(1) The coal lump mined at the coal mining face can automatically slide down, which simplifies the loading and transportation of the coal face, but the falling coal lump and gangue are easy to wash down the support, hurt people, and bring unsafe factors to production
(2) The vertical component force of the steep coal seam roof pressure acting on the support or coal pillar is smaller than that of the gently sloping coal seam, while the component force acting along the slope is larger. The roof and floor of the coal seam may slide along the slope, and the support stability is greater , Thus increasing the complexity of mining and support work.
(3) The operations of pedestrians, material transportation, coal falling, support, and goaf treatment at the coal mining face are relatively difficult, which increases the difficulty of mechanized coal mining. In order to overcome these difficulties, a variety of coal mining face layouts and advancing directions have been adopted, thus forming various coal mining methods.
(4) The arrangement of a set of uphills in the mining area can replace the transportation uphill in the gently inclined coal seam with the coal-slide hole, and use the material hole instead of the track uphill; for safety, set pedestrian eyes in sections; Suppose slipping eyes.
(5) Generally speaking, steep coal seams have experienced strong geological changes, with complex geological structures and poor surrounding rock conditions; coupled with the slow advancement of coal mining faces, the recovery rate is low. Therefore, the strike length of the mining area is smaller than that of a gently inclined coal seam.
2. Longwall mining method for steep coal seam strike
1) Inverted bench mining method The coal mining face is in the shape of an inverted bench
Advantages: simple roadway layout; low driving rate; simple ventilation system; high recovery rate; strong adaptability to geological conditions.
Disadvantages: multiple processes, complex operations, high labor intensity, high support technology requirements; large consumption of pit wood; large coal dust, poor safety; low technical and economic indicators.
Application: Coal seams with large occurrence changes and thickness less than 2m.
2) Longwall mining method with protruding and false oblique strike
Features: The coal mining face is arranged in a straight line in a downward and pseudo-inclined direction, advancing along the strike; the sectioned horizontal intensive cutting top and gangue are used to isolate the goaf from the mining space; the working face is blasted in sections to drop coal and the coal is transported by itself.
Advantages: The pseudo-inclined straight line layout of the working face reduces the sliding speed of coal and gangue, which is beneficial to prevent the support from falling down and hurt people, and improves the safe production conditions of the working face; at the same time, the pseudo-inclined straight line layout of the working face improves the top of the working face. The force condition of the floor has relatively increased stability, and there will be no large-area bottom push and roof cracks; under the same vertical height of the section, the effective utilization rate of the working face is higher than that of the step coal mining method. The ventilation situation near the coal wall of the working face and the realization of mechanized coal mining provide conditions; the dense segmental strikes mainly play the role of retaining gangue except for cutting the roof, intercepting the gangue in the goaf, and forming a gap between the working space and the roof caving area. The natural filling zone makes the basic top pressure lag far behind, slows down the effect of the basic top pressure, and reduces the loss of face pillars and maintenance workload.
Problem: The mining workload of the pillars in the working face is still heavy, and the operation is not convenient enough for the workers; the triangle area under the dense pillars is poorly ventilated and easy to accumulate gas; when the roof of the coal seam is sprayed with water, the working environment is relatively poor. It is suitable for low-gas coal seams with an inclination angle above 40 degrees, moderately stable roofs, easy slicing of the coal walls, and low-gas coal seams with a working face height of no more than 2m, or unstable steep thin and medium-thick coal seams that are not suitable for mining with pseudo-inclined flexible shields.
3. Coal mining method with false inclined flexible shield support
Pseudo-inclined flexible shield coal mining method-the mining face is arranged in a straight line and pseudo-inclined, and advances along the direction, and a flexible shield is used to isolate the goaf. Workers mine coal under the shield.
Stoping work-preparation, stoping, finishing
Prepare for mining. Widen the return air tunnel to the roof and floor of the coal seam, dig a trench 5m from the cut hole, and install a shield support in the widened return air tunnel
Adjust the slope of the shield support The slope of the shield support is adjusted into a pseudo-inclined working face with a slope of 25-30 degrees
Normal mining 1) Extend the long shield support—coal mining—remain on the coal chute and remove the support in the return airway. Connect the long shield support 8 ----10m beyond the upper exit. 2) Coal mining—blast mining—charge -In-line-blasting (one-time blasting or segmental blasting in full face) to discharge coal (laying chute)-adjusting support, etc. 3) Dismantle the support—Lay the support flat at the lower end of the mining face and leave a space of 1.2m high. Remove the support
Ending 1) Dig two ends uphill on the side of the stop line—the distance between the strikes is 8-----10m, and pass through them with crosscuts. 2) The bracket is installed at the end uphill, and no longer extends 3) The front end bracket is lowered along with the coal mining. , The pseudo-bevel gradually becomes smaller, and remove the excess bracket at the upper end, and lay the bracket flat. 4) Remove all brackets
Advantages: Roadway layout and production system are simple, and the excavation rate is low; the working space is separated from the mined area by the shielding bracket, which greatly simplifies the complicated and heavy roof management work, and creates good conditions for safe production and three-shift coal discharge; working face The self-slipping transportation of coal reduces the heavy coal labor. High economic and technical effect.
Disadvantages: the support structure is not perfect, the width cannot be adjusted, and the adaptability is poor; if there is water spray, the working conditions are poor; only a group of workers work in the mining face, and the process needs to be improved; the coal dust is large and the working environment is poor; the support removal is troublesome; the gangue cannot be eliminated , Reduce coal quality.
4. Horizontal subsection top coal mining method
Horizontal subsection top coal mining method—In steep coal seams, it is divided into several sections according to a certain height. The coal mining face is arranged at the bottom of the section, the coal at the bottom face is first extracted, and then the upper top coal is discharged.
5. Storage coal mining method Advantages: simple roadway layout and simple production system. There are few procedures, high efficiency, and the withdrawal procedure is eliminated. Pit wood consumption is small. Labor intensity has been reduced. Disadvantages: low recovery rate; difficult to ensure coal quality; strict requirements for use conditions.
6. Horizontal slicing and inclined slicing coal mining method. The horizontal slicing coal mining method is to divide the steep thick coal seam into several layers that are level with the horizontal plane. The thickness of each layer is 2-3M, and the thickness of each layer is 2-3M. Arrange the mining roadway in the layer to form a coal mining face, and then successively carry out the mining, and the coal mining face advances along the strike. The slicing method of the inclined slicing mining method is to form an angle of 25-30 degrees between the layer and the horizontal plane.
