shaft sinking

shaft sinking,

excavation from the surface of an opening in the earth. Shafts, which are generally vertical, are usually distinguished from tunnelstunnel,
underground passage usually made without removing the overlying rock or soil. Although tunnels are approximately horizontal, they must be built with sufficient gradient for proper drainage.
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, which are horizontal. Little difficulty is experienced in shaft sinking through solid rock, which contains little water. When loose, water-bearing strata have to be contended with, careful shoring and sealing of the shaft lining become necessary, and pumping facilities are needed. Shafts are usually circular or rectangular and are generally lined with wood, masonry, concrete, steel, or cast iron. Shafts sunk in loose water-bearing soils, where there is great external pressure on the shaft sides, are nearly always circular; rectangular shafts with wood lining are often used in mining work, as the shafts are frequently of a temporary nature. Shaft sinking through rock is generally accomplished by blasting. When the loose surface material has been removed, holes are drilled, and the charges are placed and are fired by electricity. The broken rock is removed and the process is repeated. In an ordinary rectangular shaft the lining consists of timbers 8 or 12 in. (20 or 30 cm) square placed horizontally around the shaft. Shafts of a more permanent nature are generally circular in form and lined with cast iron or with concrete masonry 1 to 2 ft (30–61 cm) thick, built in sections as the work advances. When excessive quantities of water are met with, cast-iron tubbing is sometimes used. This consists of heavy cast-iron rings made in segments, with flanges for connecting, and bolted together in place. Cement grout is forced into the space between the outside of the tubbing and the surrounding earth to form a seal. Shaft sinking by the freezing process in very watery soil is accomplished by sinking pipes in the area to be excavated and circulating brine at low temperature in them until the earth is frozen and hard so that it can be excavated in the same manner as rock. In the grouting method, liquid cement is forced into the water-bearing earth under very high pressure. On mixing with the water, the cement solidifies the adjacent area, and it is removed by drilling and blasting as with rock.

shaft sinking

[′shaft ‚siŋk·iŋ]
(mining engineering)
Excavating a shaft downward, usually from the surface, to the workable coal or ore.
References in periodicals archive ?
Shaft sinking will get underway in June 2016 if KGHM opts for two shafts, or in September 2016 if it decides on the single shaft option.
At the Hira- Buddini and Uti gold mine,the second phase of mining by shaft sinking and mine development is in process.
gravity drainage of umg, starboard shaft sinking and metalwork.
This includes the shaft sinking at the proposed mine site near Whitby, and to construct the 23-mile tunnel and associated shafts for the mineral transport system that will take the mined polyhalite to Teesside.
Longyear's influence in contract diamond drilling, geological services and shaft sinking in the early part of the 20[sup.
Shaft sinking operation may consume up to 60% of time of the underground mine development stage (Unrug 1992).
A South African mine has developed an innovative method for shaft sinking by combining technologies for soft ground digging, drilling, blasting and raise-boring.
Part of the Holystone Group - which also boasts plant hire, waste and recycling and demolition divisions - Holystone Ltd specialises in a range of services including drainage, road building, wet well construction, shaft sinking and tunnelling, pumping station construction, concrete structure construction and hard landscaping for leading civil engineering companies and local authorities.
The 36-foot diameter entry shaft at the Seymour end was originally to be driven at the filtration plant area, but preliminary drilling revealed that there was about 300 feet of saturated sands and gravels that would have made for tough shaft sinking.
SHAFT sinking was plagued by flooding problems, and German mining experts with specialised freezing equipment were brought in.