Board & Pillar
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This document discusses two mining methods: step mining and post-pillar mining. Step mining involves creating horizontal floors to allow equipment use for deposits that are too steeply inclined. Post-pillar mining uses regularly spaced pillars to extract inclined deposits between 20-55 degrees and allows filling of the mined space. It also discusses considerations for gallery dimensions, pillar dimensions and configurations, recovery strategies, equipment used, and operational aspects of board and pillar mining.
Board & Pillar
- 5. Step mining It is an adaptation for the case where the dip of the ore body is too big (15o to 30o) to use equipment on tires at the same time that its thickness is relatively small (2 - 5 m). A special orientation of transit and stops galleries creates areas with horizontal floor, allowing the use of equipment on tires. The mining progresses from top to bottom in mining panels.
- 6. Post-pillar mining Applies to inclined deposits with dip between 20o and 55o. Have large vertical dimension, and filling the mined space suffers (backfilling). The filler maintains the stable rock (minimizes columns) and serves as a working platform for the next slice.
- 7. Regularly spaced openings formed orthogonal arrangement of square or rectangular pillars. Development (axle) and exploitation (panel) galleries usually have very similar characteristics. several parallel galleries and connected by dashes. is a method for mining large-scale, with the various panels can be conducted simultaneously. the basic unit of mining is the panel that defines the area to be worked and ventilated.
- 8. a) Dimensions of the Galleries b) Dimensions of the Pillars c) Mining with or without Recovery of Pillars d) Number of Front Panel
- 9. Widths of 5 to 6m are currently quite common. Height is limited by the thickness of mineable coal (in SC deposits, the section is rectangular with heights ranging from 2.0m to 3.5m approx.). Condition shoring ceiling. Interfere in operational and safety aspects. Dimensions are used to calculate the recovery of mining.
- 10. Currently, for the Boards and Pillars method to succeed, the deposits must have a particular geological condition of the roof. The overlying layer extracts the coal must be self-sustaining condition or be likely anchor (there are several types of anchoring screws ceiling, with different principles of operation - see Appendix A). Due to costs, shoring bows with metal or wood are used only in restricted areas of the mine.
- 11. influence on operational aspects (e.g. transport distances) and safety (risk of collapse of pillars). influence the recovery of mining. Types of pillars. o square and rectangular pillars o chain pillars (internal pillars of the mining panel) o barrier pillars (the pillars of safety)
- 12. most common ways of mining ... Recovery strategies pillars .
- 14. Equipment to aid in the recovery of pillars.
- 15. Example of Mining panel
- 17. The advancement of the panel is done through several parallel galleries (5 galleries or more, depending on the mine) connected by dashes. It takes more fronts in conventional mode (drill- blast-load-haul) and less fronts with continuous miner. The use of continuous miner least affects the roof and pillars and produces thin material.
- 18. Moderate to high productivity (m3 / man-hour) Moderate cost of mining (relative cost = 0.3) Moderate to high production rate High degree of flexibility (allows variable thickness in the ore); method easily modifiable; may operate simultaneously on multiple levels Allows high degree of mechanization Selective method, lets leave waste material on site. Does not require much anticipated development. It can be operated on multiple fronts.
- 19. Reasonable recovery without extraction of pillars (50- 65% on carbon), low dilution (10-20%). Comparing with Longwall. LW is Pratic. inflexible, requires greater investment, there is subsidence on the surface, has high yields (must be a market for the product!), LW global recoveries are possibly lower than B & P with pillar recovery. In direct comparison with Longwall. LW is Pratic. inflexible, requires greater investment, there is subsidence on the surface, has high yields (must be a market for the product!), LW global recoveries are often lower than B & P with pillar recovery.
- 20. Requires ongoing maintenance of the roof and eventually the pillars. The tension in the open spaces increases with depth. Significant capital investment for extensive mechanization. Loss of ore in pillars. In the case of B & P in hard rock, it may be difficult to achieve good ventilation to dilute contaminants in due to low air velocity panel in large open spaces. Requires good technical and engineering support.