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Inclined layering, layered co-mining, layered separate mining — Black Diamond Report
The inclined coal seam longwall descending caving mining method has become one of the core technologies widely used in the coal mining industry because it can adapt to most geological conditions of inclined thick coal seams and achieve efficient resource recovery. The core logic of this technology is to reduce the difficulty of single mining in thick coal seams through "layered control." Among the three key steps—inclined layering, simultaneous layered mining, and sequential layered mining—these are crucial in determining mining efficiency and safety factors. The following will analyze them one by one.
1. Basic Core: Inclined Layering — Breaking "Thick Coal Seams" into "Thin Coal Layers"
If a thick coal seam is mined at full height in one go, it will face problems such as difficult roof control, high support pressure, and high risk of goaf collapse. The inclined layering technology was developed to solve this pain point. Its core definition is: dividing a thick inclined coal seam into several thin layers of appropriate thickness (usually 2-3 meters, specifically determined by coal seam hardness and support equipment capability) along the direction parallel to the coal seam plane, and then mining layer by layer in a "descending" order from top to bottom.
In practice, inclined layering must follow two key principles: first, the layering interface must remain parallel to the original coal seam plane to avoid damaging the coal seam integrity and reduce the risk of roof and floor collapse; second, after mining the upper layer, the naturally collapsed rock from its roof (called "caving gangue") should be used to fill the goaf, providing cushioning support for mining the lower layer and reducing roof pressure on the lower working face. This "layered mining and caving bottom protection" model not only reduces the technical difficulty of single mining but also achieves over 90% resource utilization of thick coal seams through stepwise recovery. It is the fundamental premise for subsequent simultaneous and sequential layered mining.
2. Simultaneous Layered Mining
When a coal mine has sufficient equipment configuration and management capability, and the geological conditions of the coal seam are stable, simultaneous layered mining becomes the preferred solution to increase output. Its official definition is: within the same mining section (i.e., the same coal seam block), two or more working faces of upper and lower layers mine coal simultaneously with a certain safety distance staggered.
The core points of simultaneous layered mining are:
Safety Distance Control: The staggered distance between the upper and lower layered working faces must be strictly calculated, usually based on the roof caving step distance (generally 10-20 meters), to avoid impact on the lower working face caused by the collapse of the upper goaf and prevent disturbance of the upper residual coal by the lower mining.
Coordinated Management: The mining speed, support rhythm, and transportation system of the upper and lower layers must be synchronized and coordinated. For example, if the upper working face uses a fully mechanized support, the lower layer must plan the support installation positions in advance to avoid equipment conflicts.
Applicable Scenarios: More suitable for coal seams with thickness of 5-8 meters, inclination of 15-30° (moderate inclination angle facilitating equipment movement), and stable roof and floor. It can improve section mining efficiency by 30%-50%, but requires high technical management level and equipment matching capability of the mine.
3. Sequential Layered Mining
If a coal mine has insufficient equipment, complex geological conditions (such as interbedded gangue layers, easily broken roof and floor), sequential layered mining (also commonly known in the industry as "big peeling") is a more robust choice. Its definition is: within the same mining section, completely mining all coal resources of one layer first, and after the roof of that layer has fully collapsed and stabilized, then moving on to mine the next layer.
The notable features of sequential layered mining are:
Simplified Process: No need to coordinate multiple working faces simultaneously; each stage only focuses on mining, support, and goaf treatment of a single layer. The operation process is simpler and requires lower technical demands on the on-site management team.
Controllable Risk: Due to the long interval between layered mining, the collapsed gangue in the upper goaf can be fully compacted, providing a more stable working environment for the lower layer mining. It is especially suitable for coal seams with soft roof and floor prone to roof fall accidents.
Disadvantages and Suitability: The drawback is a longer mining cycle and overall section output lower than simultaneous layered mining; it is more suitable for coal seams with thickness of 3.5-6 meters, fluctuating geological conditions (such as local faults), or small to medium-sized mines, enabling orderly recovery of thick coal seam resources while ensuring safety.
4. Technical Value and Development Direction
The inclined coal seam longwall descending caving mining method builds a flexible technical system for thick coal seam mining through the "splitting mindset" of inclined layering, the "efficiency mindset" of simultaneous layered mining, and the "safety mindset" of sequential layered mining — coal mines can "tailor" according to their equipment conditions and geological situations: choose simultaneous layered mining to increase output when geology is good and equipment is sufficient, or choose sequential layered mining to control risks when conditions are complex and stability is pursued.
With the coal mining industry moving towards intelligent transformation, this technology is continuously upgrading: some mines have now achieved intelligent coal cutting on layered working faces and remote monitoring of roof pressure, optimizing layered thickness and mining intervals through data-driven methods to further balance efficiency and safety. In the future, with the deep integration of 5G and IoT technologies, the inclined coal seam longwall descending caving mining method will become more efficient and safer, providing stronger technical support for the development of thick coal seam resources.
