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Sublevel stoping..Underground mining methods

Considerations on the sublevel stoping method; Conditions for application of the deposit; Characteristic of Sublevel Stoping Method; Application; Development; Sublevel overhand; Sublevel underhand; Slot; Configuration of stopes; Drawpoints

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Sublevel stoping..Underground mining methods

  1. 1. Hassan Z. Harraz hharraz2006@yahoo.com 2014- 2015 This material is intended for use in lectures, presentations and as handouts to students, and is provided in Power point format so as to allow customization for the individual needs of course instructors. Permission of the author and publisher is required for any other usage. Please see hharraz2006@yahoo.com for contact details. Topic 4: Underground Mining Methods  Sublevel Stoping
  2. 2. Outline of Topic 4:  Considerations on the method  Conditions for application of the deposit  Characteristic of Sublevel Stoping Method  Application  Development  Sublevel overhand  Sublevel underhand  Slot  Configuration of stopes  Drawpoints Prof. Dr. H.Z. Harraz Presentation sublevel stoping 2 We will explore all of the above in Topic 4.
  3. 3. Sublevel Stoping Considerations on the method:  the sublevel stoping is considered a method of extracting medium to large scale;  other names for the method (variations): bighole open stoping, long-hole stoping or blasthole Prof. Dr. H.Z. Harraz Presentation sublevel stoping 3 Conditions for application of the deposit: ore resistance: moderate to high; resistance of the host rocks: moderate to high; forms: tabular or lenticular, thick (6 - 30m) and extensive lengthwise; Diving:> 45, preferably 60o- 90o; good uniformity of grades and thicknesses of ore; depth of deposit: moderate, preferably <1.2 km. Sublevel stoping: configuration method in stopes where the ore is detonated by drilling a fan or parallel; large part of the ore is removed from the stope as it is being detonated, leaving open stope.
  4. 4. Two versions are common to the method:  using range in drilling (drilling-ring version) in production, with small diameter holes (2-3 "). Here, only the drift to be the sublevel open stope when working on;  using parallel drilling (drilling parallel) production, with holes of large diameter (up to 7.5 ") and greater length. Should open a horizontal slot for positioning the drill. This is done by extending the drift of the sublevel across the width of the stope. Prof. Dr. H.Z. Harraz Presentation sublevel stoping 4
  5. 5. Drilling in range (drilling-ring) Prof. Dr. H.Z. Harraz Presentation sublevel stoping 5
  6. 6. Figura 2 Drilling Parallel (multi-level blasthole stoping) Prof. Dr. H.Z. Harraz Presentation sublevel stoping 6
  7. 7. higher panel: Bighole open stoping Prof. Dr. H.Z. Harraz Presentation sublevel stoping 7
  8. 8. Characteristic of Sublevel Stoping Method Advantages  Moderate to high productivity per man-shift  Moderate cost of mining (relat = 0.4.)  Moderate to high production rate  Suitable for mechanization  Low exposure to unsafe conditions  Possibility of simultaneous unit operations  Average recovery (75%); Moderate dilution (up to 20%). Disadvantages  Slow, complex and costly development (though part is done in ore)  Non-selective method  Drilling long production requires careful alignment (small deviation in the holes)  Great takedowns that can cause excessive vibration, displacement of air and structural damage. Prof. Dr. H.Z. Harraz Presentation sublevel stoping 8
  9. 9. Applications:  the main criterion for application of the method is to have competent ore and host rocks, regular limits for ore and the footwall slope that exceeds the angle of repose of the fragmented ore (> 50o overall)  drill, blast and loading are done independently;  large of the ore is removed from the stope as it is being detonated, leaving open stope.  a recovery can reach 100% if the pillars can be recovered; Prof. Dr. H.Z. Harraz Presentation sublevel stoping 9
  10. 10. The method can operate with Sublevel (fig. Below) without recovery or Pillars. Prof. Dr. H.Z. Harraz Presentation sublevel stoping 10
  11. 11. Development:  ramps and shafts in the footwall,  transport routes to the base of the stope ore, ore or barren;  ascending raises are open for connection to the upper level and allow ventilation;  development options : overhand ... underhand ... Prof. Dr. H.Z. Harraz Presentation sublevel stoping 11
  12. 12. Sublevel underhand 12 Sublevel overhand Prof. Dr. H.Z. Harraz Presentation sublevel stoping
  13. 13. Sublevel underhand Prof. Dr. H.Z. Harraz Presentation sublevel stoping 13
  14. 14. Prof. Dr. H.Z. Harraz Presentation sublevel stoping 14 Slot initial  Slot: is a space for the expansion of the rock where the extraction begins in the conventional stope sublevel. The slot will the level of the roof of the stope extraction. It is opened from a slot raise and can be executed in various ways (conventional raising, raise boring, ...).
  15. 15. Developmental sequence? slot raisethe stope Prof. Dr. H.Z. Harraz Presentation sublevel stoping 15
  16. 16. development slot… Stope production … Prof. Dr. H.Z. Harraz Presentation sublevel stoping 16
  17. 17. Configuration of stopes The geometry of the stopes and pillars must adapt to the spatial distribution of ore. The position and shape of the pillars will be determined by geotechnical data and rock mechanics models for mass. The height of the stope typically not exceeding 150 meters away. Later fill (backfill) of stopes can be done to improve support walls and pillars of recovery. Cablebolts are also used. Prof. Dr. H.Z. Harraz Presentation sublevel stoping 17
  18. 18. Configuration of stopes Intermediate slopes of the stope can cause stability problems in the hangingwall and dilution. Prof. Dr. H.Z. Harraz Presentation sublevel stoping 18
  19. 19. Configuration of stopes The definition of the total volume and shape of the stopes is of great importance for the SLOS method. Larger stopes generally have higher productivity, but higher risk of instability and increased dilution. One of the most commonly used options for scaling stopes is the empirical approach called "stability graph method." In this method, an open stope stability is expressed in terms of two parameters: hydraulic radius (RH) and the stability number N ', both relating to the ceiling or side wall of the excavation. Referências para o “stability graph method”: The stability graph method for open-stope design; Underground Min. Methods: Eng. Fundamentals and International Case Studies, 2001, W.A.Hustrulid & R.Bullock; Chapter 60, p. 513-520. Prof. Dr. H.Z. Harraz Presentation sublevel stoping 19
  20. 20. Configuration of stopes The hydraulic radius of a face or side wall of the stope equals the surface area of the face divided by its perimeter. RH = Área / Perímetro O número de estabilidade N’ é obtido a partir de:  Q is the rate of geomechanics classification of NGI (Norwegian Geotechnical Institute) Prof. Dr. H.Z. Harraz Presentation sublevel stoping 20
  21. 21. Configuration of stopes... Graph of stability: the values ​​calculated for HR and N 'define whether a particular face will be stable, unstable or suffer subsidence (caving). Prof. Dr. H.Z. Harraz Presentation sublevel stoping 21
  22. 22. Configuration of stopes... Fitting parameters A, B and C : Prof. Dr. H.Z. Harraz Presentation sublevel stoping 22
  23. 23. Configuration of stopes... Example usage method: Consider a situation where stopes are excavated in competent rock (RQD = 60), with four dominant joint sets (Jn = 15), which are planar and without alteration (Ja = 1.0; Jr = 1.0). The ore shows the uniaxial compressive strength of 120 MPa, while the maximum stress is 24 MPa (determined by numerical models). The critical side to be analyzed is shown on the next slide. The set of critical joints forms an angle of 85o with the face of the stope, which has dimensions of 15m x 38m. Tuning parameters: Fator A = 0.45; Fator B = 0.85; Fator C = 7.0. 5.5 7630 1538 7.100.785.045.0 0.1 0.1 15 60 '      HR N Prof. Dr. H.Z. Harraz Presentation sublevel stoping 23
  24. 24. Configuration of stopes... The point (N ', SR) graph shows the stability at the boundary between the stable and unstable areas, which indicates that the hydraulic radius is maximum 5.5 wise dimension to be applied to the stope. Prof. Dr. H.Z. Harraz Presentation sublevel stoping 24
  25. 25. Configuration of stopes... The point (N '= 10.7, HR = 5.5) in the stability chart Prof. Dr. H.Z. Harraz Presentation sublevel stoping 25
  26. 26. Configuration of stopes... If the stope has a setting that indicates high possibility of subsidence, there are alternative design to make it more stable. Example: lower your volume or leave pillars inside the stope ... Prof. Dr. H.Z. Harraz Presentation sublevel stoping 26
  27. 27. Configuration of stopes... Another alternative to improve stability: strengthen (s) face (s) of the stope with cablebolts ... The stopes can also receive fill (backfill) after extraction of the ore. Prof. Dr. H.Z. Harraz Presentation sublevel stoping 27
  28. 28. Filling of stopes* ...  Fits relief and redistribution of stresses in the massif.  To be left empty, the stopes can begin a process of caving when they started is hard to stop and much of the infrastructure and mine reserves can be lost.  Common fillers are CHF (cemented hydraulic fill) and Paste Fill. One advantage of the paste fill is that there is little water to drain, compared to CHF.  Once the stope is empty, it is blocked at the bottom, with the construction of barricades (bulkheads).  It is also equipped with vents which connect with the inner part of the stope and allow water drainage.  The stope filling in a short period of time produces great pressure on bulkheads, which can rupture, with risk to facilities and staff.  Paste fill is safer because in the event of breakage of bulkheads material spreads over shorter distances, due to the lower amount of water in the composition. *Sloane, L., 2010. Sublevel open stoping: design of the O640, L651 and N659 sublevel open stopes in the 3000 orebody of the Mount Isa copper mines, Queensland, Australia. Department of Mining, University of Pretoria. Prof. Dr. H.Z. Harraz Presentation sublevel stoping 28
  29. 29. Configuration of stopes To investigate the differences between the stope volume designed / performed and estimate the dilution involved in the process, there are now the CMS (Caving Monitoring System) devices. Laser devices are making a scan of the internal void of the stope. A definition for dilution: Dilution = (sterile ton produced) / (ton of ore Planned) Prof. Dr. H.Z. Harraz Presentation sublevel stoping 29
  30. 30. Configuration of stopes The number of stopes, dimensions and mining sequence must relate to the programmed so that suffice 60% to 80% of the stopes developed to perform it daily production. The remaining stopes should be available for production if any of the planned stopes are out of action. Stopes also provide extra flexibility to maintain a relatively constant level of power plant. Inside view of a stope already plowed  Prof. Dr. H.Z. Harraz Presentation sublevel stoping 30
  31. 31. Drawpoints Excerpted from: Wise, J. J., 1982, “Loading and hauling equipment for use in caving and sublevel stoping”. Design and operation of caving and sublevel stoping mines. p.683-691. Drawpoints are basic elements of development methods used in sublevel stoping, sublevel caving, block caving, shrinkage, VCR and others. Can be positioned: -in sublevels production when using sublevel caving-; -na base level or ore body, when it is used block caving, sublevel stoping and VCR. Prof. Dr. H.Z. Harraz Presentation sublevel stoping 31
  32. 32. Drawpoints Prof. Dr. H.Z. Harraz Presentation sublevel stoping 32
  33. 33. Sublevel Stoping Predominant equipment used in loading and drawpoints until the 50s transport: scrapers / slushers overshot loaders transport on rails. Characteristics of these devices: long-Change from a local operation to another, which can lead to low utilization; -facilities designed to operate in horizontal planes, which should be interconnected by raising. Raises are expensive and unsuitable for moving large equipment. Prof. Dr. H.Z. Harraz Presentation sublevel stoping 33
  34. 34. After the 50s:  ramps access between levels, using equipment on tires (LHD's) and higher productivity, to load / transport of ores, personnel and materials.  Drilling long and large diameter, causing the mechanization of the structural development of the drawPoint. Consequences of the use of equipment on tires:  Need galleries with larger section because the equipment is larger;  development of spiral ramps which slope must be carefully chosen;  the management of highways, drainage, better ventilation and more technical mechanical maintenance. Sublevel Stoping Prof. Dr. H.Z. Harraz Presentation sublevel stoping 34
  35. 35. As LHD’s:  allowed the development of access ramps steeper (lower development costs) and provided better equipment utilization;  used along with drills on tires, simplify development of drawpoints, reducing the execution time (see Figs. next slide). Sublevel Stoping Prof. Dr. H.Z. Harraz Presentation sublevel stoping 35
  36. 36. Basic factors for the system on tires:  drawpoint drifts enough to LHD's width;  Ventilation suitable for diesel;  large interval between drawpoints; Long-system transport in various dimensions, or orepass leading to long transport system in lower levels;  Several sites distant work (for diesel engines). Sublevel Stoping Prof. Dr. H.Z. Harraz Presentation sublevel stoping 36

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