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Rules of Thumb for Mining and processing

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    Given: 8
    Sinking shaft.

    *
    Area: Schedule
    * • From time of award to the start of sinking a timber shaft will be approximately five months. A circular concrete shaft may take three months longer unless the shaft collar and headframe are completed in advance. Source: Tom Anderson
    * • The average rate of advance for shaft sinking will be two-thirds of the advance in the best month (the one everyone talks about). Source: Jim Redpath
    *
    Area: Hoist
    * • The hoist required for shaft sinking needs approximately 30% more horsepower than for skipping the same payload at the same line speed. Source: Jack de la Vergne
    * • Without slowing the rate of advance, a single drum hoist is satisfactory to sink to a depth of 1,500 feet at five buckets per foot, 2,000 feet at four buckets per foot, and 2,500 feet at 3½ buckets per foot. For deeper shafts, a double drum hoist is required to keep up with the shaft mucker. Source: Jack de la Vergne
    *
    Area: Bucket
    * • For sinking a vertical shaft, the bucket size should be at least big enough to fill six for each foot of shaft to be sunk; five is better. Source: Marshall Hamilton
    * • For the bucket to remain stable when detached on the shaft bottom, its height should not exceed its diameter by more than 50%. Source: Jim Redpath
    * • Tall buckets can be used safely if the clam is used to dig a hole in the muck pile for the buckets. Source: Bill Shaver
    * • A bucket should not be higher than 7½ feet for filling with a standard Cryderman clam (which has an 11-foot stroke). Source: Bert Trenfield
    * • A bucket should not be higher than 6 feet when mucking with a 630, which has a 6-foot-6-inch discharge height. Source: Alan Provost
    * • You can load a tall bucket using a 630 if you slope the muck pile so that the bucket sits at an angle from the vertical position. Source: Fern Larose
    * • In a wet shaft, the contractor should be able to bail up to 10 buckets of water per shift without impeding his advance. Source: Paddy Harrison
    *
    Area: Water Pressure
    * • For any shaft, the water pressure reducing valves should be installed every 250 feet. "Toilet tank" reducers are more reliable than valves and may be spread further apart. Source: Peter van Schaayk
    * • Water pressure reducing valves may be eliminated for shaft sinking if the water line is slotted and the drill water is fed in batch quantities. Source: Allan Widlake and Jannie Mostert
    *
    Area: Compressed Air
    * • One thousand cfm of compressed air is needed to blow the bench with a two-inch blowpipe. Source: Bill Shaver
    * • Twelve hundred cfm of compressed air is needed to operate a standard Cryderman clam properly. Source: Bill Shaver
    *
    Area: Shaft Stations
    * • The minimum station depth at a development level to be cut during shaft sinking is 50 feet. Source: Tom Goodell
    * • A shaft station will not be cut faster than 2,000 cubic feet per day with slusher mucking. It may be cut at an average rate of 3,500 cubic feet per day with an LHD mucking unit. Source: Jim Redpath
    *
    Area: Circular Shaft
    * • The minimum (finished) diameter of a circular shaft for bottom mucking with a 630-crawler loader is 18 feet. Source: Tom Goodell
    * • For a circular concrete shaft, the minimum clearance between the sinking stage and the shaft walls is 10 inches. Source: Henry Lavigne
    * • A circular concrete lined shaft sunk in good ground will have an average overbreak of 10 inches or more, irrespective of the minimum concrete thickness. Source: Jim Redpath
    * • For a rope guide system in a shaft being sunk to a moderate depth, the minimum clearance between a conveyance (bucket and crosshead) and a fixed obstruction is 12 inches and to another bucket is 24 inches. At the shaft collar, the clearance to a fixed obstruction may be reduced to 6 inches due to slowdown, or less with the use of fairleads or skid plates. In a deep shaft, 18-24 inches is required to clear a fixed obstruction and 30-36 inches is required between buckets, depending on the actual hoisting speed. These clearances assume that the shaft stage hangs free and the guide ropes are fully tensioned when hoisting buckets. Source: Various
    * • When hoisting at speeds approaching 3,000 fpm (15m/s) on a rope guide system, the bonnet of the crosshead should be grilled instead of being constructed of steel plate to minimize aerodynamic sway. Source: Morris Medd
    * • The maximum rate at which ready-mix concrete will be poured down a 6-inch diameter slick line is 60 cubic yards per hour. Source: Marshall Hamilton
    *
    Area: Timber Shaft
    * • For a timber shaft, the minimum clearance to the wall rock outside wall plates and end plates should be 6 inches; the average will be 14 inches in good ground. Source: Alan Provost
    * • For a timber shaft that encounters squeezing ground, the minimum clearance outside wall plates and end plates should be 12 inches. Source: Dan Hinich
    * • For a timber shaft, the blocking should not be longer than two feet without being pinned with rock bolts to the wall rock. Source: Jim Redpath

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    Thumbs Up
    Received: 89
    Given: 8
    Mining Field: Backfill
    Area: General
    The cost of backfilling will be near 20% of the total underground operating cost. Source: Bob Rappolt
    The capital cost of a paste fill plant installation is approximately twice the cost of a conventional hydraulic fill plant of the same capacity. Source: Barrett, Fuller, and Miller
    If a mine backfills all production stopes to avoid significant delays in ore production, the daily capacity of the backfill system should be should be at least 1.25 times the average daily mining rate (expressed in terms of volume). Source: Robert Currie
    The typical requirement for backfill is approximately 50% of the tonnage mined. It is theoretically about 60%, but all stopes are not completely filled and tertiary stopes may not be filled at all. Source: Ross Gowan
    It is common to measure the strength of cemented backfill as if it were concrete (i.e. 28 days), probably because this time coincides with the planned stope turn-around cycle. Here it should be noted that while concrete obtains over 80% of its long- term strength at 28 days, cemented fill might only obtain 50%. In other words, a structural fill may have almost twice the strength at 90 days as it had at 28 days. Source: Jack de la Vergne
    Area: Hydraulic Fill
    Because the density of hydraulic fill when placed is only about half that of ore, unless half the tailings can be recovered to meet gradation requirements, a supplementary or substitute source of fill material is required. Source: E. G. Thomas
    Area: Cemented Rock Fill
    A 6% binder will give almost the same CRF strength in 14 days that a 5% binder will give in 28 days. This rule is useful to know when a faster stope turn-around time becomes necessary. Source: Joel Rheault
    As the fly ash content of a CRF slurry is increased above 50%, the strength of the backfill drops rapidly and the curing time increases dramatically. A binder consisting of 35% fly ash and 65% cement is deemed to be the optimal mix. Source: Joel Rheault
    The size of water flush for a CRF slurry line should be 4,000 US gallons. Source: George Greer
    The optimum W/C ratio for a CRF slurry is 0.8:1, but in practice, the water content may have to be reduced when the rock is wet due to ice and snow content of quarried rock or ground water seepage into the fill raise. Source: Finland Tech
    The actual strength of CRF placed in a mine will be approximately 2/3 the laboratory value that is obtained from standard 6 inch diameter concrete test cylinders, but will be about 90% of the value obtained from 12 inch diameter cylinders. Source: Thiann Yu
    Area: Paste Fill
    Only about 60% of mill tailings can be used for paste fill over the life of a mine because of the volume increase, which occurs as a result of breaking and comminuting the ore. Source: David Landriault
    Experience to date at the Golden Giant mine indicates that only 46% of the tailings produced can be used for paste fill. Source: Jim Paynter
    Very precise control of pulp density is required for gravity flow of paste fill. A small (1-2%) increase in pulp density can more than double pipeline pressures (and resistance to flow). Source: David Landriault
    40% of paste fill distribution piping may be salvaged for re-use. Source: BM&S Corporation

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  3. [23]
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    Thumbs Up
    Received: 89
    Given: 8
    *
    Mining Field: Exploration Geology and Ore Reserves
    *
    Area: Discovery
    * • It takes 25,000 claims staked to find 500 worth diamond drilling to find one mine. Source: Lorne Ames
    * • On average, the time between discovery and actual start of construction of a base metal mine is 10 years; it is less for a precious metal mine. Source: J.P. Albers
    *
    Area: Costs
    * • The amount expended on diamond drilling and exploration development for the purposes of measuring mineral reserves should approximately equal 2% of the gross value of the metals in the reserves. Source: Joe Gerden
    *
    Area: Bulk Sample
    * • The minimum size of a bulk sample, when required for a proposed major open pit mine, is in the order of 50,000 tons (with a pilot mill on site). For a proposed underground mine, it is typically only 5,000 tons. Source: Jack de la Vergne
    *
    Area: Ore Reserve Estimate
    * • The value reported for the specific gravity (SG) of an ore sample on a metallurgical test report is approximately 20% higher than the correct value to be employed in the resource tonnage calculation. Source: Jack de la Vergne
    *
    Area: Ore Resource Estimate
    * • To determine "inferred" or "possible" reserves, it is practice to assume that the ore will extend to a distance at least equal to half the strike length at the bottom of measured reserves. Another rule is that the largest horizontal cross section of an ore body is half way between its top and bottom. Source: H. E. McKinstry
    * • In the base metal mines of Peru and the Canadian Shield, often a zonal mineralogy is found indicating depth. At the top of the ore body sphalerite and galena predominate. Near mid-depth, chalcopyrite becomes significant and pyrite appears. At the bottom, pyrite, and magnetite displace the ore. Source: H. E. McKinstry
    * • In gold mines, the amount of silver that accompanies the gold may be an indicator of depth. Shallow gold deposits usually have relatively high silver content while those that run deep have hardly any. Source: James B. Redpath
    * • As a rule of thumb, I use that 2P (Probable) reserves are only such when drill spacing does not exceed five to seven smallest mining units (SMU). Open pit mining on 15m benches could have an SMU of 15m by 15m by 15m. Underground, an SMU would be say 3m by 3m by 3m (a drift round). Source: René Marion
    *
    Area: Strike and Dip
    * • The convention for establishing strike and dip is always the Right Hand Rule. With right hand palm up, open and extended, point the thumb in the down-dip direction and the fingertips provide the strike direction. Source: Mike Neumann

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    Thumbs Up
    Received: 89
    Given: 8
    *
    Area: General
    * • An underground trackless mine may require 10 tons of fresh air to be circulated for each ton of ore extracted. The hottest and deepest mines may use up to 20 tons of air for each ton of ore mined. Source: Northern Miner Press
    * • A factor of 100 cfm per ore-ton mined per day can be used to determine preliminary ventilation quantity requirements for most underground mining methods. Hot mines using ventilation air for cooling and mines with heavy diesel equipment usage require more air. Uranium mines require significantly higher ventilation quantities, up to 500 cfm per ton per day. Block cave and large-scale room and pillar mining operations require significantly lower ventilation quantities, in the range of 20 to 40 cfm per ton per day for preliminary calculations. Source: Scott McIntosh
    * • Ventilation is typically responsible for 40% of an underground mine's electrical power consumption. Source: CANMET
    * • If the exhaust airway is remote from the fresh air entry, approximately 85% of the fresh air will reach the intended destinations. If the exhaust airway is near to the fresh air entry, this can be reduced to 75%, or less. The losses are mainly due to leaks in ducts, bulkheads, and ventilation doors. Source: Jack de la Vergne
    * • Mine Resistance - For purposes of preliminary calculations, the resistance across the mine workings between main airway terminals underground (shafts, raises, air drifts, etc.) may be taken equal to one-inch water gauge. Source: Richard Masuda
    * • Natural pressure may be estimated at 0.03 inches of water gage per 10 degrees Fahrenheit difference per 100 feet difference in elevation (at standard air density). Source: Robert Peele
    *
    Area: Airways
    * • The maximum practical velocity for ventilation air in a circular concrete production shaft equipped with fixed (rigid) guides is 2,500 fpm (12.7m/s). Source: Richard Masuda
    * • The economic velocity for ventilation air in a circular concrete production shaft equipped with fixed (rigid) guides is 2,400 fpm (12m/s). If the shaft incorporates a man-way compartment (ladder way) the economic velocity is reduced to about 1,400 fpm (7m/s). Source: A.W.T. Barenbrug
    * • The maximum velocity that should be contemplated for ventilation air in a circular concrete production shaft equipped with rope guides is 2,000 fpm and the recommended maximum relative velocity between skips and airflow is 6,000 fpm. Source: Malcom McPherson
    * • The "not-to-exceed" velocity for ventilation air in a bald circular concrete ventilation shaft is 4,000 fpm (20m/s). Source: Malcom McPherson
    * • The typical velocity for ventilation air in a bald circular concrete ventilation shaft or a bored raise is in the order of 3,200 fpm (16m/s) to be economical and the friction factor, k, is normally between 20 and 25. Source: Jack de la Vergne
    * • The typical velocity for ventilation air in a large raw (unlined) ventilation raise or shaft is in the order of 2,200 fpm (11m/s) to be economical and the friction factor, k, is typically between 60 and 75. Source: Jack de la Vergne
    * • The typical range of ventilation air velocities found in a conveyor decline or drift is between 500 and 1,000 fpm. It is higher if the flow is in the direction of conveyor travel and is lower against it. Source: Floyd Bossard
    * • The maximum velocity at draw points and dumps is 1,200 fpm (6m/s) to avoid dust entrainment. Source: John Shilabeer
    * • A protuberance into a smooth airway will typically provide four to five times the resistance to airflow as will an indent of the same dimensions. Source: van den Bosch and Drummond
    * • The friction factor, k, is theoretically constant for the same roughness of wall in an airway, regardless of its size. In fact, the factor is slightly decreased when the cross-section is large. Source: George Stewart
    *
    Area: Ducts
    * • For bag duct, limiting static pressure to approximately 8 inches water gage will restrict leakage to a reasonable level. Source: Bart Gilbert
    * • The head loss of ventilation air flowing around a corner in a duct is reduced to 10% of the velocity head with good design. For bends up to 30 degrees, a standard circular arc elbow is satisfactory. For bends over 30 degrees, the radius of curvature of the elbow should be three times the diameter of the duct unless turning vanes inside the duct are employed. Source: H.S. Fowler
    * • The flow of ventilation air in a duct that is contracted will remain stable because the air-flow velocity is accelerating. The flow of ventilation air in a duct that is enlarged in size will be unstable unless the expansion is abrupt (high head loss) or it is coned at an angle of not more than 10 degrees (low head loss). Source: H. S. Fowler
    *
    Area: Fans
    * • Increasing fan speed by 10% may increase the quantity of air by 10%, but the power requirement will increase by 33%. Source: Chris Hall
    * • The proper design of an evasée (fan outlet) requires that the angle of divergence not exceed 7 degrees. Source: William Kennedy
    *
    Area: Air Surveys
    * • For a barometric survey, the correction factor for altitude may be assumed to be 1.11 kPa/100m (13.6 inches water gage per thousand feet). Source: J.H. Quilliam
    *
    Area: Clearing Smoke
    * • The fumes from blasting operations cannot be removed from a stope or heading at a ventilation velocity less than 25 fpm (0.13m/s). A 30% higher air velocity is normally required to clear a stope. At least a 100% higher velocity is required to efficiently clear a long heading. Source: William Meakin
    * • The outlet of a ventilation duct in a development heading should be advanced to within 20 duct diameters of the face to ensure it is properly swept with fresh air. Source: J.P. Vergunst
    * • For sinking shallow shafts, the minimum return air velocity to clear smoke in a reasonable period of time is 50 fpm (0.25m/s). Source: Richard Masuda
    * • For sinking deep shafts, the minimum return air velocity to clear smoke in a reasonable period of time is 100 fpm (0.50m/s). Source: Jack de la Vergne
    * • For sinking very deep shafts, it is usually not practical to wait for smoke to clear. Normally, the first bucket of men returning to the bottom is lowered (rapidly) through the smoke. Source: Morris Medd
    *
    Area: Mine Air Heating
    * • To avoid icing during winter months, a downcast hoisting shaft should have the air heated to at least 50C. (410 F.). A fresh air raise needs only 1.50C. (350 F.). Source: Julian Kresowaty
    * • When calculating the efficiency of heat transfer in a mine air heater, the following efficiencies may be assumed.
    90% for a direct fired heater using propane, natural gas or electricity
    80% for indirect heat transfer using fuel oil
    Source: Various
    * • When the mine air is heated directly, it is important to maintain a minimum air stream velocity of approximately 2,400 fpm across the burners for efficient heat transfer. If the burners are equipped with combustion fans, lower air speeds (1,000 fpm) can be used. Source: Andy Pitz
    * • When the mine air is heated electrically, it is important to maintain a minimum air stream velocity of 400 fpm across the heaters. Otherwise, the elements will overheat and can burn out. Source: Ed Summers
    *
    Area: Heat Load
    * • The lowest accident rates have been related to men working at temperatures below 70 degrees F and the highest to temperatures of 80 degrees and over. Source: MSHA
    * • Auto compression raises the dry bulb temperature of air by about 1 degree Celsius for every 100m the air travels down a dry shaft. (Less in a wet shaft.) The wet bulb temperature rises by approximately half this amount. Source: Various
    * • At depths greater than 2,000m, the heat load (due to auto compression) in the incoming air presents a severe problem. At these depths, refrigeration is required to remove the heat load in the fresh air as well as to remove the geothermal heat pick-up. Source: Noel Joughin
    * • At a rock temperature of 50 degrees Celsius, the heat load into a room and pillar stope is about 2.5 kW per square meter of face. Source: Noel Joughin
    * • In a hot mine, the heat generated by the wall rocks of permanent airways decays exponentially with time � after several months it is nearly zero. There remains some heat generated in permanent horizontal airways due to friction between the air and the walls. Source: Jack de la Vergne
    * • A diesel engine produces 200 cubic feet of exhaust gases per Lb. of fuel burned and consumption is approximately 0.45 Lb. of fuel per horsepower-hour. Source: Caterpillar and others
    * • Normally, the diesel engine on an LHD unit does not run at full load capacity (horsepower rating); it is more in the region of 50%, on average. In practice, all the power produced by the diesel engines of a mobile equipment fleet is converted into heat and each horsepower utilized produces heat equivalent to 42.4 BTU per minute. Source: A.W.T.Barenbrug
    * • The heat load from an underground truck or LHD is approximately 2.6 times as much for a diesel engine drive as it is for electric. Source: John Marks
    * • The efficiency of a diesel engine can be as high as 40% at rated RPM and full load, while that of an electric motor to replace it is as high as 96% at full load capacity. In both cases, the efficiency is reduced when operating at less than full load. Source: Various
    * • Normally, the electric motor on an underground ventilation fan is sized to run at near full load capacity and it is running 100% of the time. In practice, all the power produced by the electric motor of a booster fan or development heading fan is converted into heat and each horsepower (33,000 foot-Lb./minute) produces heat equivalent to 42.4 BTU per minute. (1 BTU = 778 foot-Lbs.) Source: Jack de la Vergne
    * • Normally, the electric motor on a surface ventilation fan is sized to run at near full load capacity and it is running 100% of the time. In practice, about 60% of the power produced by the electric motors of all the surface ventilation fans (intake and exhaust) is used to overcome friction in the intake airways and mine workings (final exhaust airways are not considered). Each horsepower lost to friction (i.e. static head) is converted into heat underground. Source: Jack de la Vergne
    * • Heat generated by electrically powered machinery underground is equal to the total power minus the motive power absorbed in useful work. The only energy consumed by electric motors that does not result in heat is that expended in work against gravity, such as hoisting, conveying up grade, or pumping to a higher elevation. Source: Laird and Harris
    *
    Area: Air Conditioning and Refrigeration
    * • In the Republic of South Africa, cooling is required when the natural rock temperature reaches the temperature of the human body (98.6 degrees F). Source: A.W.T. Barenbrug
    * • A rough approximation of the cooling capacity required for a hot mine in North America is that the TR required per ton mined per day is 0.025 times the difference between the natural rock temperature (VRT) and 95 degrees F. For example, a 2,000 ton per day mine with a VRT of 140 degrees F. at the mean mining depth will require approximately 0.025 x 45 x 2,000 = 2,250 TR. Source: Jack de la Vergne

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    تاريخ التسجيل: Mar 2007
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    Thumbs Up
    Received: 89
    Given: 8
    Lateral Development and Ramps
    Area: General
    Laser controls should be used in straight development headings that exceed 800 feet (240m) in length. Source: Tom Goodell
    The overall advance rate of a lateral drive may be increased by 30% and the unit cost decreased by 15% when two headings become available. Source: Bruce Lang
    Area: Trackless Headings
    The minimum width for a trackless heading is 5 feet wider than the widest unit of mobile equipment. Source: Fred Edwards
    The back (roof) of trackless headings in hard rock should be driven with an arch of height equal to 20% of the heading width. Source: Kidd Mine Standards
    The cost to slash a trackless heading wider while it is being advanced is 80% of the cost of the heading itself, on a volumetric basis. Source: Bruce Lang
    For long ramp drives, the LHD/truck combination gives lower operating costs than LHDs alone and should be considered on any haul more than 1,500 feet in length. Source: Jack Clark
    LHD equipment is usually supplemented with underground trucks when the length of drive exceeds 1,000 feet. Source: Fred Edwards
    With ramp entry, a satellite shop is required underground for mobile drill jumbos and crawler mounted drills when the mean mining depth reaches 200m below surface. Source: Jack de la Vergne
    With ramp and shaft entry, a main shop is required underground when the mean mining depth reaches 500m below surface. Source: Jack de la Vergne
    A gradient of 2% is not enough for a horizontal trackless heading. It ought to be driven at a minimum of 2½% or 3%. Source: Bill Shaver
    The minimum radius of drift or ramp curve around which it is convenient to drive a mobile drill jumbo is 75 feet. Source: Al Walsh
    For practical purposes, a minimum curve radius of 50 feet may be employed satisfactorily for most ramp headings. Source: John Gilbert
    The gathering arm reach of a continuous face-mucking unit should be 2 feet wider than the nominal width of the drift being driven. Source: Jim Dales
    Footwall drifts for trackless blasthole mining should be offset from the ore by at least 15m (50 feet) in good ground. Deeper in the mine, the offset should be increased to 23m (75 feet) and for mining at great depth it should be not less than 30m (100 feet). Source: Jack de la Vergne
    Ore passes should be spaced at intervals not exceeding 500 feet (and waste passes not more than 750 feet) along the draw point drift, with LHD extraction. Source: Jack de la Vergne
    The maximum practical air velocity in lateral headings that are travelways is approximately 1,400 fpm. Even at this speed, a hard hat may be blown off when a vehicle or train passes by. At higher velocities, walking gets difficult and road dust becomes airborne. However, in pure lateral airways, the air velocity may exceed 3,000 fpm. Source: Various
    The typical range of ventilation air velocities found in a conveyor decline or drift is between 500 and 1,000 fpm. It is higher if the flow is in the direction of conveyor travel and is lower against it. Source: Floyd Bossard
    The maximum velocity at draw points and dumps is 1,200 fpm (6m/s) to avoid dust entrainment. Source: John Shilabeer
    Area: Track Headings
    Track gage should not be less than ½ the extreme width of car or motor (locomotive). Source: MAPAO
    The tractive effort, TE (Lbs.) for a diesel locomotive is approximately equal to 300 times its horsepower rating. Source: John Partridge
    Wood ties should have a length equal to twice the track gage, be at least ¼ inch thicker than the spike length, and 1 3/8 times spike length in width. Source: MAPAO
    Typical gradients for track mines are 0.25% and 0.30%. Source: MAPAO
    A minimum clearance of three feet should be designed between the outside of the rails and the wall of the drift to permit safe operation of a mucking machine when driving the heading. Source: MAPAO

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  6. [26]
    alshangiti
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    تاريخ التسجيل: Mar 2007
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    Thumbs Up
    Received: 89
    Given: 8

    رد: Rules of Thumb for Mining and processing

    *
    Area: Wood Headframe
    * • The maximum height of a wood headframe is 110 feet. The maximum rope size for a wood headframe is 1.25 inches diameter, which corresponds to an 8-foot or 100-inch diameter double-drum hoist. Source: Jack de la Vergne
    *
    Area: Steel Headframe
    * • A headframe (for a ground mounted hoist) should be designed with the backlegs at an angle of 60 degrees from the horizontal and the rope flight from the hoist at an angle of 45 degrees. Source: Mine Plant Design, Staley, 1949
    * • It is better to design a headframe (for a ground mounted hoist) such that the resultant of forces from the overwound rope falls about 1/3 the distance from the backleg to the backpost. Source: Mine Plant Design, Staley, 1949
    * • No members in a steel headframe should have a thickness less than 5/16 of an inch. Main members should have a slenderness ratio (l/r) of not more than 120; secondary members not more than 200. Source: Mine Plant Design, Staley, 1949
    * • Main members of a modern steel headframe may have a slenderness ratio as high as 160 meeting relevant design codes and modern design practice. Source: Steve Boyd
    *
    Area: Steel Headframe versus Concrete Headframe
    * • The cost of a steel headframe increases exponentially with its height while the cost of a concrete headframe is nearly a direct function of its height. As a result, a steel headframe is less expensive than a concrete headframe, when the height of the headframe is less than approximately 160 feet (at typical market costs for structural steel and ready-mix concrete). Source: Jack de la Vergne
    * • At the hoist deck level of a tower mount headframe for Koepe hoisting, the maximum permissible lateral deflection (due to wind sway, foundation settlement, etc.) is 3 inches. (This may favor a concrete headframe.) Source: R. L. Puryear
    * • A concrete headframe will weigh up to ten times as much as the equivalent steel headframe. (This may favor the steel headframe when foundations are in overburden or the mine site is in a seismic zone.) Source: Steve Boyd
    *
    Area: Headframe Bins
    * • To determine the live load of a surface bin for a hard rock mine, the angle of repose may be assumed at 35 degrees from the horizontal (top of bin) and the angle of drawdown assumed at 60 degrees. Source: Al Fernie
    * • A bin for a hard rock mine will likely experience rat-holing (as opposed to mass flow) if the ore is damp, unless the dead bed at the bin bottom is covered or replaced with a smooth steel surface at an angle of approximately 60 degrees from the horizontal. Source: Jennike and Johanson
    * • The live-load capacity of the headframe ore bin at a small mine (where trucking of the ore is employed) may be designed equal to a day's production. For a mine of medium size, it can be as little as one-third of a day's production. For a high capacity skipping operation, the headframe should have a conveyor load-out, either direct to the mill or elevated to separate load-out bins remote from the headframe. A conveyor load-out requires a small surge bin at the headframe of live load capacity approximately equal to the payload of 20 skips. Source: Various

    0 Not allowed!


    المهندس / يحيى بن محمد الشنقيطى

  7. [27]
    alshangiti
    alshangiti غير متواجد حالياً

    مشرف وإستشاري هندسة المناجم


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    تاريخ التسجيل: Mar 2007
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    وسام مشرف متميز

    Thumbs Up
    Received: 89
    Given: 8

    رد: Rules of Thumb for Mining and processing

    Mining Field: Rock Mechanics

    Area: Ground Stress
    • The vertical stress may be calculated on the basis of depth of overburden with an accuracy of ± 20%. This is sufficient for engineering purposes. Source: Z.T. Bieniawski
    • Discs occur in the core of diamond drill holes when the radial ground stresses are in excess of half the compressive rock strength. Source: Obert and Stephenson
    • The width of the zone of relaxed stress around a circular shaft that is sunk by a drill and blast method is approximately equal to one-third the radius of the shaft excavation. Source: J. F. Abel

    Area: Ground Control
    • The length of a rock bolt should be one-half to one-third the heading width. Source: Mont Blanc Tunnel Rule (c.1965)
    • In hard rock mining, the ratio of bolt length to pattern spacing is normally 1½:1. In fractured rock, it should be at least 2:1. (In civil tunnels and coalmines, it is typically 2:1.) Source: Lang and Bischoff (1982)
    • In mining, the bolt length/bolt spacing ratio is acceptable between 1.2:1 and 1.5:1. Source: Z.T. Bieniawski (1992)
    • In good ground, the length of a roof bolt can be one-third of the span. The length of a wall bolt can be one-fifth of the wall height. The pattern spacing may be obtained by dividing the rock bolt length by one and one-half. Source: Mike Gray (1999)
    • The tension developed in a mechanical rock bolt is increased by approximately 40 Lbs. for each one foot-pound increment of torque applied to it. Source: Lewis and Clarke
    • A mechanical rock bolt installed at 30 degrees off the perpendicular may provide only 25% of the tension produced by a bolt equally torqued that is perpendicular to the rock face, unless a spherical washer is employed. Source: MAPAO
    • For each foot of friction bolt (split-set) installed, there is 1 ton of anchorage. Source: MAPAO
    • The shear strength (dowel strength) of a rock bolt may be assumed equal to one-half its tensile strength. Source: P. M. Dight
    • The thickness of the beam (zone of uniform compression) in the back of a bolted heading is approximately equal to the rock bolt length minus the spacing between them. Source: T.A. Lang
    • Holes drilled for resin bolts should be ¼ inch larger in diameter than the bolt. If it is increased to 3/8 inch, the pull out load is not affected but the stiffness of the bolt/resin assembly is lowered by more than 80%, besides wasting money on unnecessary resin. Source: Dr. Pierre Choquette
    • Holes drilled for cement-grouted bolts should be ½ to 1 inch larger in diameter than the bolt. The larger gap is especially desired in weak ground to increase the bonding area. Source: Dr. Pierre Choquette

    Area: Mine Development
    • Permanent underground excavations should be designed to be in a state of compression. A minimum safety factor (SF) of 2 is generally recommended for them. Source: Obert and Duval
    • The required height of a rock pentice to be used for shaft deepening is equal to the shaft width or diameter plus an allowance of five feet. Source: Jim Redpath

    Area: Stope Pillar and Design
    • A minimum SF of between 1.2 and 1.5 is typically employed for the design of rigid stope pillars in hard rock mines. Source: Various
    • For purposes of pillar design in hard rock, the uniaxial compressive strength obtained from core samples should be reduced by 20-25% to obtain a true value underground. The reduced value should be used when calculating pillar strength from formulas relating it to compressive strength, pillar height, and width (i.e. Obert Duval and Hedley formulas). Source: C. L. de Jongh
    • The compressive strength of a stope pillar is increased when later firmly confined by backfill because a triaxial condition is created in which s3 is increased 4 to 5 times (by Mohr's strength theory). Source: Donald Coates

    Area: Subsidence
    • In block caving mines, it is typical that the cave is vertical until sloughing is initiated after which the angle of draw may approach 70 degrees from the horizontal, particularly at the end of a block. Source: Fleshman and Dale
    • Preliminary design of a block cave mine should assume a potential subsidence zone of 45-degrees from bottom of the lowest mining level. Although it is unlikely that actual subsidence will extend to this limit, there is a high probability that tension cracking will result in damage to underground structures (such as a shaft) developed within this zone. Source: Scott McIntosh
    • In hard rock mines employing backfill, any subsidence that may occur is always vertical and nothing will promote side sloughing of the cave (even drill and blast). Source: Jack de la Vergne

    Area: Rockbursts
    • 75% of rockbursts occur within 45 minutes after blasting. Source: Swanson and Sines
    • Seismic events may be the result of the reactivation of old faults by a new stress regime. By Mohr-Coulomb analysis, faults dipping at 30 degrees are the most susceptible; near vertical faults are the safest. Source: Asmis and Lee
    • In burst prone ground, top sills are advanced simultaneously in a chevron ('V') pattern. Outboard sills are advanced in the stress shadow of the leading sill with a lag distance of 24 feet. Source: Luc Beauchamp

    0 Not allowed!


    المهندس / يحيى بن محمد الشنقيطى

  8. [28]
    alshangiti
    alshangiti غير متواجد حالياً

    مشرف وإستشاري هندسة المناجم


    الصورة الرمزية alshangiti


    تاريخ التسجيل: Mar 2007
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    وسام مشرف متميز

    Thumbs Up
    Received: 89
    Given: 8
    : Compressed Air


    Area: Air Intake


    The area of the intake duct should be not less than ½ the area of the low-pressure cylinder of a two-stage reciprocating compressor. Lewis and Clark
    Area: Air Line Losses


    At 100 psi, a 6-inch diameter airline will carry 3,000 cfm one mile with a loss of approximately 12 psi. Franklin Matthias
    At 100 psi, a 4-inch diameter airline will carry 1,000 cfm one mile with a loss of approximately 12 psi. Franklin Matthias
    A line leak or cracked valve with an opening equivalent to 1/8-inch (3 mm) diameter will leak 25 cfm (42m3/min.) at 100 psig (7 bars). Lanny Pasternack
    In a well-managed system, the air leaks should not exceed 15% of productive consumption. Lanny Pasternack
    Many older mines waste as much as 70% of their compressed air capacity through leakage. Robert McKellar
    Drilling requires a 25-psi air drop across the bit for cooling to which must be added the circulation loss for bailing of cuttings in the borehole at a velocity of 5,000 fpm, or more. Reed Tool
    Except in South Africa, pneumatic drills are usually designed to operate at 90 psig (6.2 bars). Their drilling speed will be reduced by 30% at 70 psig (4.8 bars). Christopher Bise
    A line oiler reduces the air pressure by 5 psi. Ingersoll-Rand
    An exhaust muffler can increase the required air pressure by 5 psi, or more. Morris Medd
    A constant speed compressor designed to be fed at 60 cycles (hertz) will operate at 50 cycles, but experience a reduction in capacity of about 17%. Jack de la Vergne
    Area: Altitude


    A constant speed compressor (or booster) underground will require 1% more horsepower for every 100m of depth below sea level. Atlas Copco
    Auto-compression will increase the gage pressure of a column of air in a mineshaft by approximately 10% for each 3,000 feet of depth (11% for each 1,000m). Jack de la Vergne
    The compressed air from a constant speed compressor will have 1% less capacity to do useful work for every 100m above sea level that it is located. Atlas Copco
    Area: Cooling


    A water-cooled after-cooler will require approximately 3 USGPM per 100 cfm of air compressed to 100 psig. Ingersoll-Rand
    Area: Power


    The horsepower required for a stationary single-stage electric compressor is approximately 28% that of its capacity, expressed in cfm (sea level at 125 psig). Lyman Scheel
    The horsepower required for a portable diesel air compressor is approximately 33% that of its capacity, expressed in cfm (sea level at 125 psig). Franklin Matthias
    To increase the output pressure of a two-stage compressor from 100 to 120 psig requires a 10% increase in horsepower (1% for each 2 psig). Ingersoll-Rand
    Area: Receiver


    The primary receiver capacity should be six times the compressor capacity per second of free air for automatic valve unloading. Atlas Copco
    The difference between automatic valve unloading and loading pressure limits should not be less than 0.4 bar. Atlas Copco

    0 Not allowed!


    المهندس / يحيى بن محمد الشنقيطى

  9. [29]
    alshangiti
    alshangiti غير متواجد حالياً

    مشرف وإستشاري هندسة المناجم


    الصورة الرمزية alshangiti


    تاريخ التسجيل: Mar 2007
    المشاركات: 1,472

    وسام مشرف متميز

    Thumbs Up
    Received: 89
    Given: 8
    Cost Estimating

    Area: Budget Estimates

    • An allowance (such as 15%) should be specifically determined and added to the contractor's formal bid price for a mining project to account for contract clauses relating to unavoidable extra work, delays, ground conditions, over-break, grouting, de-watering, claims, and other unforeseen items. Jack de la Vergne

    Area: Cost of Estimating

    • A detailed estimate for routine, repetitive work (i.e. a long drive on a mine level) may cost as little as 0.5% of the project cost. On the other hand, it may cost up to 5% to adequately estimate projects involving specialized work, such as underground construction and equipment installation. Various

    Area: Cost of Feasibility Study

    • The cost of a detailed feasibility study will be in a range from 0.5% to 1.5% of the total estimated project cost. Frohling and Lewis
    • The cost of a detailed or "bankable" feasibility study is typically in the range of 2% to 5% of the project, if the costs of additional (in-fill) drilling, assaying, metallurgical testing, geotechnical investigations, etc. are added to the direct and indirect costs of the study itself. R. S. Frew

    Area: Engineering, Procurement, and Construction Management

    • The Engineering, Procurement, and Construction Management (EPCM) cost will be approximately 17% for surface and underground construction and 5% for underground development. Jack de la Vergne

    Area: Haulage

    • The economical tramming distance for a 5 cubic yard capacity LHD is 500 feet and will produce 500 tons per shift, for an 8-yard LHD, it is 800 feet and 800 tons per shift. Sandy Watson
    • Haulage costs for open pit are at least 40% of the total mining costs; therefore, proximity of the waste dumps to the rim of the pit is of great importance. Frank Kaeschager

    Area: Miscellaneous

    • The installed cost of a long conveyorway is approximately equal to the cost of driving the drift or decline in which it is to be placed. Jack de la Vergne
    • In a trackless mine operating around the clock, there should be 0.8 journeyman mechanic or electrician on the payroll for each major unit of mobile equipment in the underground fleet. John Gilbert
    • On average, for each cubic yard of concrete measured from the neat lines on drawings, approximately 110 Lbs. of reinforcing steel and 12 square feet of forms will be required. Jack de la Vergne
    • The overall advance rate of a trackless heading may be increased by 30% and the unit cost decreased by 15% when two headings become available. Bruce Lang
    • The cost to slash a trackless heading wider while it is being advanced is 80% of the cost of the heading itself, on a volumetric basis. Bruce Lang

    Area: Overbreak

    • The amount of over-break to be estimated against rock for a concrete pour will average approximately one foot in every applicable direction, more at brows, lips, and in bad ground. Jack de la Vergne
    • On average, for each one cubic yard of concrete measured from the neat lines on drawings, there will be two cubic yards required underground, due to over-break and waste. Jack de la Vergne

    1 Not allowed!


    المهندس / يحيى بن محمد الشنقيطى

  
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