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A database of ventilation friction factors for Canadian underground mines

A database of ventilation friction factors for Canadian underground mines. Kostas Fytas, professor Charles Gagnon, graduate student Department of Mining, Metallurgical and Materials Engineering Laval University, Quebec City. June, 2008. K factor.

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A database of ventilation friction factors for Canadian underground mines

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  1. A database of ventilation friction factors for Canadian underground mines Kostas Fytas, professor Charles Gagnon, graduate student Department of Mining, Metallurgical and Materials Engineering Laval University, Quebec City June, 2008

  2. K factor • Empirical friction factor expressing friction losses • Includes shock losses • Very important in simulations of ventilation networks • It can be computed from Atkinson’s formula : • K friction factor K (Kg/m³) • H pressure drop measured underground (Pa) • A area of airway (m²) • L length of airway (between two measuring points) (m) • P perimeter of airway (m) • V air velocity (m /s)

  3. Previous work

  4. Problem • Many ventilation engineers still use the K factors by McElroy (1935) • McElroy measured them in the following conditions: • small openings (2-6 m2), extremely rough rock surfaces • obstacles (rail transport), timber supported • not representative of modern conditions • Modern conditions: • much larger openings (10-15m2), better drilling & blasting methods, smoother walls, supported by rockbolts or shotcrete • Measuring K factors is tedious & requires expensive equipment

  5. Objectives of database of K factors • To help ventilation planners to better estimate K factors according to specific conditions • Create a database of K factors & a search engine that is • user friendly • rapid • integrated images (to characterize wall roughness) • drilling patterns • detailed description of local conditions

  6. Ventilation survey • The following mines participated in the project : • Beaufor (Val-Senneville), • Bell-Allard (Matagami), • Bouchard-Hébert (Rouyn-Noranda), • Doyon, (Rouyn-Noranda), • Géant-Dormant (Amos), • Laronde (Cadillac), • Louvicourt (Louvicourt), • Mouska (Rouyn-Noranda), • Niobec (St-Honoré), • Raglan (Katinniq)

  7. K factor measurement • K friction factor (Kg/m³) • H pressure drop(Pa) • A area of airway(m²) • L length of airway(m) • P perimeter of airway (m) • V air velocity (m /s)

  8. Calculation of head losses (H) • H is calculated from Bernouilli’s equation (energy conservation):  Heads at point 1 =  Heads at point 2 + losses: HS1 + HZ1 + HV1 = HS2 + HZ2 + HV2 + Losses • HS1 et HS2: statique heads • HZ1 et HZ2 : potential heads • HV1 et HV2 : velocity heads 1 2

  9. Dry and wet bulb temperatures (ts , th) Psychrometric properties of mine air : Sling psychrometer Air density () and Relative humidity () • K factor standardization : • Specific K factor (Ks) • Standardised K factor (KN) KN = KS * air Nm/air in-situ

  10. Pressure survey (H) • Two modern SETRA 370 altimeters were used • Resolution of 1 foot or 3,59 Pascal • Precision of 0,02%.

  11. Area (A) and perimeter (P) of section Photography Digitization • Precision of 1% to 2%

  12. Distance between 2 points (L) : Resolution of 1 cm and precision of 0,1%.

  13. Air velocity (V) • Anemometer Extech instrument • Resolution of 1 m/sec • Precision of 1%. • Continuous traversing of section

  14. 1 - V > 2 m/s 2 - L > 40 m 3 – No air loss • Minimal measuring conditions 361 K factors were measured → 139 were retained

  15. Variables • Support type • Wall roughness, drilling pattern • Curvature • Obstacles • The database is an empirical tool to estimate K factors according to specifique conditions • The database can be used to do : • Ventilation planning of a new mine • Ventilation planning of an existing mine

  16. RESULTS • Statistics • Search engine

  17. Regular airways

  18. Small airways • Small vein deposits • openings of 2-2,5m x 2-2,5m

  19. Inclined haulage drifts

  20. Spiral ramps

  21. Ventilation raises 1 - Conventional 2 - Alimak 3 – Raise boring

  22. Typical K factors

  23. Example of photos

  24. Example of photos

  25. Example of photos

  26. CONCLUSIONS • K factors are very important in ventilation network simulations • K factors are difficult to measure • A user friendly database with built in photographs • The database allows the rapid estimation of K factors with a good precision • The use of photographs allows the user to estimate K factors according to his specific conditions • The database can be used to do : • Ventilation planning of a new mine • Ventilation planning of an existing mine

  27. Acknowledgements • The following mines thatparticipated in the project : • Beaufor (Val-Senneville), Bell-Allard (Matagami), Bouchard-Hébert (Rouyn-Noranda), Doyon, (Rouyn-Noranda), Laronde (Cadillac), Louvicourt (Louvicourt), Géant-Dormant (Amos), Mouska (Rouyn-Noranda), Niobec (St-Honoré), Raglan (Katinniq). • IRSST • QuebecMining Association (AMQ)

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