Stoping (mining method)
Encyclopedia
Stoping is the removal of the wanted ore
from an underground mine
leaving behind an open space known as a stope. Stoping is used when the country rock
is sufficiently strong not to cave into the stope, although in most cases artificial support is also provided. As mining progresses the stope is often backfilled with tailings
, or when needed for strength, a mixture of tailings and cement.
In the past stoping took place with manual tools or by fire-setting
; later gunpowder
was used, and from the 19th century various other explosives and power-tools came into use.
In old mines, stopes frequently collapse at a later time, leaving craters at the surface. They are an unexpected danger when records of underground mining have been lost with the passage of time.
s of tin
, the stopes become long narrow near-vertical spaces, which, if one reaches the surface is known as a gunnis or coffen. A common method of mining such vertical ore bodies is stull stoping, see below.
When the ore body is more or less horizontal, various forms of room and pillar
stoping, cut and fill
, or longwall mining
can take place.
in Cornwall was caused by failure of the stulls holding up a huge weight of waste rock.
ore
bodies (70°—90°). In shrinkage stoping, mining proceeds from the bottom upwards, in horizontal slices (similar to cut and fill mining), with the broken ore being left in place for miners to work from. Because blasted rock takes up a greater volume than in situ
rock (due to swell factor), some of the blasted ore (approximately 40%) must be removed to provide working space for the next ore slice. Once the top of the stope is reached all the ore is removed from the stope. The stope may be backfilled or left empty depending on the rock conditions.
ing.
Ore
An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
from an underground mine
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...
leaving behind an open space known as a stope. Stoping is used when the country rock
Country rock (geology)
Country rock is a geological term meaning the rock native to an area. It is similar and in many cases interchangeable with the terms basement and wall rocks....
is sufficiently strong not to cave into the stope, although in most cases artificial support is also provided. As mining progresses the stope is often backfilled with tailings
Tailings
Tailings, also called mine dumps, slimes, tails, leach residue, or slickens, are the materials left over after the process of separating the valuable fraction from the uneconomic fraction of an ore...
, or when needed for strength, a mixture of tailings and cement.
In the past stoping took place with manual tools or by fire-setting
Fire-setting
Fire-setting is a method of mining used since prehistoric times up to the Middle Ages. Fires were set against a rock face to heat the stone, which was then doused with water...
; later gunpowder
Gunpowder
Gunpowder, also known since in the late 19th century as black powder, was the first chemical explosive and the only one known until the mid 1800s. It is a mixture of sulfur, charcoal, and potassium nitrate - with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer...
was used, and from the 19th century various other explosives and power-tools came into use.
In old mines, stopes frequently collapse at a later time, leaving craters at the surface. They are an unexpected danger when records of underground mining have been lost with the passage of time.
Types of stoping
A stope can be created in a variety of ways, depending on the geology of the ore body being mined. It is common to dig shafts vertically downwards to reach the ore body and then drive horizontal levels through it. Stoping then takes place from these levels, in its simplest form as overhand and underhand stoping, which refer to the removal of ore from above or below the level, respectively. In steeply-dipping ore bodies, such as lodeLode
In geology, a lode is a deposit of metalliferous ore that fills or is embedded in a fissure in a rock formation or a vein of ore that is deposited or embedded between layers of rock....
s of tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
, the stopes become long narrow near-vertical spaces, which, if one reaches the surface is known as a gunnis or coffen. A common method of mining such vertical ore bodies is stull stoping, see below.
When the ore body is more or less horizontal, various forms of room and pillar
Room and pillar
Room and pillar is a mining system in which the mined material is extracted across a horizontal plane while leaving "pillars" of untouched material to support the roof overburden leaving open areas or "rooms" underground...
stoping, cut and fill
Cut and fill
In earthmoving, cut and fill is the process of constructing a railway, road or canal whereby the amount of material from cuts roughly matches the amount of fill needed to make nearby embankments, so minimizing the amount of construction labor...
, or longwall mining
Longwall mining
Longwall mining is a form of underground coal mining where a long wall of coal is mined in a single slice . The longwall panel is typically 3–4 km long and 250–400 m wide....
can take place.
Stull stoping
Stull stoping is a form of stoping used in hardrock mining that uses systematic or random timbering ("stulls") placed between the foot and hanging wall of the vein. The method requires that the hanging wall and often the footwall be of competent rock as the stulls provide the only artificial support. This type of stope has been used up to a depth of 3,500 feet (1,077 m) and at intervals up to 12 feet (3.7 m) wide. The 1893 mining disaster at Dolcoath mineDolcoath mine
Dolcoath mine was a copper and tin mine in Camborne, Cornwall, in the United Kingdom. Its name derives from the Cornish for 'Old Ground', and it was also affectionately known as The Queen of Cornish Mines. The site is north-west of Carn Brea. Dolcoath Road runs between the A3047 road and Chapel Hill...
in Cornwall was caused by failure of the stulls holding up a huge weight of waste rock.
Shrinkage stoping
Shrinkage stope mining, or shrinkage stoping, is most suitable for steeply dippingStrike and dip
Strike and dip refer to the orientation or attitude of a geologic feature. The strike line of a bed, fault, or other planar feature is a line representing the intersection of that feature with a horizontal plane. On a geologic map, this is represented with a short straight line segment oriented...
ore
Ore
An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
bodies (70°—90°). In shrinkage stoping, mining proceeds from the bottom upwards, in horizontal slices (similar to cut and fill mining), with the broken ore being left in place for miners to work from. Because blasted rock takes up a greater volume than in situ
In situ
In situ is a Latin phrase which translated literally as 'In position'. It is used in many different contexts.-Aerospace:In the aerospace industry, equipment on board aircraft must be tested in situ, or in place, to confirm everything functions properly as a system. Individually, each piece may...
rock (due to swell factor), some of the blasted ore (approximately 40%) must be removed to provide working space for the next ore slice. Once the top of the stope is reached all the ore is removed from the stope. The stope may be backfilled or left empty depending on the rock conditions.
Long hole stoping
Long hole stoping can be the lowest cost method when large ore bodies are located in strong country rock. In operation, it is similar to an underground version of quarryQuarry
A quarry is a type of open-pit mine from which rock or minerals are extracted. Quarries are generally used for extracting building materials, such as dimension stone, construction aggregate, riprap, sand, and gravel. They are often collocated with concrete and asphalt plants due to the requirement...
ing.