Goaf Solid Backfilling for Ultra-Thick Coal Seam Mining
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Solution Overview
Problem
Current methods for mining ultra-thick coal seams, such as descending slicing and ascending backfilling slicing, face issues like repeated roof cracking, intensive strata behavior, roof caves, resource shortages, low yield, high costs, and difficulty in safety control due to frequent working face removal and low coal recovery rates.
Innovation Solution
A goaf solid backfilling technique is employed, where the ultra-thick coal seam is sliced into three layers, with the middle slice densely backfilled to serve as an artificial floor and roof, allowing for efficient coal caving and reduced working face changes, using metal meshes and cohesive materials to stabilize the backfilling layer and distribute pressure uniformly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the ultra-thick coal seam is mined using traditional slicing methods, then the coal seam can be extracted, but the working face must be frequently removed and changed, reducing mining efficiency and safety
Solution Approach 1:
The ultra-thick coal seam is divided into multiple sub-seams, with the middle sub-seam mined first and used as backfilling material. This segmentation allows the upper and lower sub-seams to be mined independently with stable working faces, eliminating the need for frequent working face removal while maintaining high mining efficiency
Solution Approach 2:
The middle sub-seam is mined and backfilled in advance to form a stable support structure before mining the upper and lower sub-seams. This preliminary action creates artificial floor and roof structures that enable subsequent mining operations to proceed with stable working faces, improving efficiency by eliminating repeated setup and teardown of mining equipment
2Productivity
If traditional slicing mining methods are used for ultra-thick coal seams, then coal extraction is achieved, but the coal recovery rate is low due to the need for multiple slices and frequent working face changes
Solution Approach 1:
By segmenting the coal seam into upper, middle, and lower sub-seams and mining them in a specific sequence, the method enables more complete extraction of coal resources. The middle sub-seam serves as backfilling material, allowing the upper and lower sub-seams to be mined with better access and control, thereby reducing coal loss and improving recovery rate
Solution Approach 2:
The middle sub-seam coal is mined and then used as backfilling material to support the upper and lower sub-seam mining operations. This approach recovers the middle sub-seam coal while utilizing it constructively, and enables more efficient recovery of the upper and lower sub-seams, overall improving the coal recovery rate
3Reliability
If the middle slice is densely backfilled to serve as artificial floor and roof, then safety is improved and working face stability is enhanced, but backfilling materials and time are consumed
Solution Approach 1:
The middle sub-seam coal that is mined is used as the backfilling material for itself, creating a self-service system. This eliminates the need to transport materials from other locations, reduces backfilling time, and provides stable support for the upper and lower sub-seam mining operations, improving working face stability without significant time penalty
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enhances safety, reduces costs, improves coal recovery rates, and simplifies the mining process by reducing the number of slices and working face changes, ensuring efficient coal caving and effective fluid isolation, thereby improving mining efficiency and safety.
Implementation Method 1
the pressure on the working face is uniformly distributed
Implementation Method 2
using metal meshes and cohesive materials to stabilize the backfilling layer
Data Source
AI summary
A method for mining an ultra-thick coal seam by utilizing a goaf solid backfilling technique is suitable for mining an ultra-thick coal seam having a thickness of 25 m-45 m. According to the method, the ultra-thick coal seam is sliced into three slices, i.e. an upper slice, a middle slice and a lower slice. First, the middle slice is subjected to solid backfilling and mining. Metal meshes are paved along a working face of the floor. The backfilling layer serves as an artificial floor for mining the upper slice and an artificial roof for mining the lower slice. Then, the upper slice is mined by the top coal caving mining based on the artificial floor formed by backfilling the goaf of the middle slice. Finally, the lower slice is mined by the top coal caving mining along the coal seam floor with the shield of the artificial roof.