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A Pile of Muck
Muck
is loose material usually rock or ore that has been fragmented as a result of blasting in a working face such as a tunnel, large underground chamber, or an open-cut excavation work site or mine.[1] Muck can also be earth or clay that has been excavated mining or tunneling.[2]

Contents

[edit] Process

The process involved in loading and hauling or transporting the muck away from the face or worksite is called "mucking." The muck is removed through a conveyance system or a muck bucket, muck box, muck cart, or muck car. If the muck is simply discharged adjacent to the work site or tunnel face and doesn’t actually deploy the involvement of mucking equipment, the process is referred to as "casting."[3]

Once the muck has been transported to the surface, it passes through the conveyor via a horizontal, inclined, vertical, or combination of horizontal and vertical route to its final destination point. The final destination point may be a waste rock or ore stock pile where the muck is then fed to a processing plant or where it may be dispatched to another final location for re-use. The movement of the muck through a horizontal or included path is called "haulage" and its movement through a steep incline or vertical path is known as "hoisting." [4] For example, surface mining excavation haulage of muck is standard, but hoisting is not as much. With underground mining, removal of muck entails both haulage and hoisting operations.

Haulage units are classified as tracked and trackless. Tracked units include ropes and locomotives that run on a track or rail whereas trackless systems consist of automobiles, conveyors and transporation through pipelines.[5]  Tracked units were prevalent in the early 1970s but since then there has been a gradual move towards trackless transportation, which is now quickly replacing tracked versions.

The actual characteristics of the muck itself will heavily influence how efficiently and effectively it can be loaded and hauled away. This includes everything from the size, shape, volume, hardness, moisture content, angle of repose, abrasiveness, and dryness or stickiness of the muck being handled. Muck also has a "bulking factor" because it increases in volume after being excavated.

If muck is sticky, it can significantly slow down the material handling process. Muck with a sticky texture is often mixed with sand to create a more workable texture. Muck that is lumpy can also affect how easily it will move along a conveyor, pipeline, or by a wheeled excavator.[6]

[edit] Equipment Used

Mucking equipment is used to load and haul muck from the worksite. Mucking units or equipment used in underground excavation such as tunneling or underground mining differ from mucking equipment used for surface excavation and surface mining with the design and size of equipment being contingent on the actual percentage of the work cycle devoted to the mucking process.

[edit] Overshot or Overhead Loader

An overshot or overhead loader is a loading machine that carries muck in a front-mounted bucket by crowding and then lifting it. Muck is picked up from the face and discharged to the rear of the machine as the bucket is designed to pass over the machine without rotating. The term overshot applies to the sudden stopping feature of the bucket as the load is discharged from the bucket and literally thrown into a haulage unit always positioned at the rear of the machine.

The first overshot loader was developed in the 1930s, originally designed for loading in narrow drift headings and draw points.[7] Overshot loaders used today still utilize the same design configuration and are track, crawler or wheel mounted and powered electrically, with diesel or compressed air. The machines are suitable for smaller sized mine openings and tunnels.

[edit] Autoloader, Hopper Loader

These are units specifically designed for direct unloading of ore and waste passes as well as for loading into trucks, dumpers, or shuttle cars. The units can be pneumatic, electric, or diesel.[8]

[edit] LHD (Load Haul Dump)

A mining vehicle used in the hauling of ore or muck with similar tasking as that of auto loaders and hopper loaders. The latest development in LHD technology is vehicle automation so that units can operate autonomously by remote control in mining environments that pose a higher risk to safety.[9]

LHDs are manufactured by more than a dozen companies with some of the more dominant manufacturers including Wagner, Eimco, Caterpillar, Joy, Atlas Copco, Equipment Miner, Schopf, and Tam-rock.

[edit] Arm loader

There are different types of arm loaders used for various mining operations.

[edit] Gathering Arm Loader (GAL)

This was first introduced in the 20th century and is a continuous-action mucking machine that features a pair of gathering arms. The arms feed the muck to a flight conveyor that in turn feeds the muck to a shuttle or mine car. The machine was designed as a versatile unit that could be easily maneuvered in coal mines. One of shortcomings of the GAL is that is does not have very good grabbing capability of fine muck or for highly abrasive rock.

[edit] Riddle Mucker

Some arm loaders are produced entirely for shaft sinking or driving in a downward position. For example, a riddle mucker, developed in the early 1950s, consists of a hoisting and traveling apparatus that operates a clamshell bucket suspended upon cables. A pneumatic tugger hoist is what operates the clamshell. The carriage of the unit is suspended on rails and located permanently next to the work shaft.

[edit] Cryderman Mucker

A cryderman mucker is a loader also developed in the 1950s that operates by means of pneumatic cylinders and a telescopic boom. This is suspended from independent hoisting system mostly located at the surface and used in rectangular, circular, and inclined mine shafts. A hydraulic version of the unit has also been developed in Canada and is powered by a self-contained hydraulic power pack and a longer boom.

[edit] Cactus-grab Mucker

A cactus-grab mucker has a pneumatic cactus grab suspended from cables and can be mounted on a carriage similar to a riddle mucker. Originally used in South African mining, its application has now been taken globally for mucking in rectangular or circular shaped shafts. The machine is mounted upon on a multi-deck sinking platform.

[edit] Backhoe Mucker

This mucker, developed by Alimak Co., is a machine that has a backhoe action rather than a clamshell or cactus grab. Powered by a hydraulic self-contained power pack, the machine can be fixed to shaft wall or suspended from the bottom of a sinking stage.

[edit] Scraper

A scraper is comprised of scraper, a wire rope for filling, and another for pulling, a return sheave, driving winch, loading slide and a power unit. There are two types of scrapers used in mucking. A box scraper is used for small size rock of low specific gravity and a hoe scraper is used mainly to load larger sized muck of higher specific gravity. The machines are also used in sand gathering plants, coal, or mineral handling plants, such as coal washeries and loading yards to transfer muck into railway wagons or trucks.

[edit] Dipper and Hydraulic Shovel

Shovels are used in the surface mining of deposits at open cast mines and mine pits. A growing trend is to use the hydraulic shovels in the mucking of very large tunnels.

[edit] Front End Loader (FEL)

The front end loader is a type of wheel loader and very similar to a LHD with the primary difference being that front end loaders are built longer, taller, and narrower than LHD units. This makes them suitable for working in small, confined spaces. They also differ from dipper shovels that have a dipper instead of a bucket to carry a load. A shovel can revolve to disengage its load from the dipper as where as FEL has to travel to discharge its bucket to a muck pile or haulage unit. Front end loaders are either mounted on wheels or crawlers and are used primarily for loading and secondarily, for hauling and casting.

[edit] Other

Other machines used in the mucking process are hydraulic excavators and backhoes.

[edit] References

  1. Tatiya, Ratan Raj. Surface and Underground Excavations: methods, techniques and equipment. A.A. Balkema, 2005.
  2. Muck. The Free Dictionary, 2008-09-29.
  3. Tatiya, Ratan Raj. Surface and Underground Excavations: methods, techniques and equipment. A.A. Balkema, 2005.
  4. Tatiya, Ratan Raj. Surface and Underground Excavations: methods, techniques and equipment. A.A. Balkema, 2005.
  5. Tatiya, Ratan Raj. Surface and Underground Excavations: methods, techniques and equipment. A.A. Balkema, 2005.
  6. Tatiya, Ratan Raj. Surface and Underground Excavations: methods, techniques and equipment. A.A. Balkema, 2005.
  7. Sundeen, Robert L.; Wenberg, Richard V. Overshot Loaders. OneMine.org, 2008-09-29.
  8. Tatiya, Ratan Raj. Surface and Underground Excavations: methods, techniques and equipment. A.A. Balkema, 2005.
  9. Load Haul Dump Equipment. Berlet Electronics Ltd., 2008-09-29.