BLASTING

From Big Medical Encyclopedia

BLASTING — the works performed for the purpose of controlled fracture, movement or structural change and a form natural (rocks, wood, ice) or artificial (concrete, a bricklaying, metals, etc.) educations, constructions or materials. Blasting is resulted by the factors, harmful to an organism, demanding holding special medical events.

Century of river are carried out with the help explosive substances (see) and blasting agents (caps detonators with the safety fuse, electrodetonators). For placement of explosive substances in the destroyed object the cavity (the shot, the well, the camera), as a rule, by drilling therefore set of processes for V.'s performance by river is often called drilling-and-blasting works is created previously.

Range of application of V. of river is extensive. They reach the largest volume in mining and construction.

Light-end products of decomposition of explosive substances contain poisonous gases, generally carbon monoxide (see) and nitric oxides (see) which can be the cause of poisoning of workers. Century of river in mining and construction are followed by formation of a large number drank (see), edges at long inhalation can promote development in workers pneumoconiosis (see); concentration of dust after explosion reaches several honeycombs and even thousands of milligrams on cubic meter of air, but in rather short time sharply decreases.

Formation of poisonous products of explosion is influenced first of all by oxygen balance of explosive substances which can be zero, positive and negative. At zero balance the volume of oxygen corresponds to its quantity necessary for oxidation of all combustible components making explosive substance. In this case at explosion only harmless end products of decomposition — carbon dioxide gas, water vapor and nitrogen shall be formed. If the amount of oxygen is not enough for full oxidation of carbon (negative balance), then carbon monoxide is formed. On the contrary, at excess of oxygen (positive balance) nitric oxides are formed. For underground mining operations explosive substances with the oxygen balance close to zero are produced (deviations no more than 1 — 1,5%). However in practice under the influence of such factors as humidity of explosive substances, existence of a paper and paraffin cover, properties of the breeds surrounding a charge, a way of detonation, etc. the amount of the formed poisonous gases is much higher.

The correct determination of the actual amount of poisonous gases allows to calculate reliably ventilation for their removal and neutralization. Airing is made so that, at least, the following rules of purity of air in excavations were respected: oxygen — not less than 20%, carbon dioxide gas — no more than 0,5%, carbon monoxide — no more than 0,0016%, nitric oxides (NO2) — 0,0002%.

A specific exit of dust at V. the river makes about 33 g on 1 kg of explosive substance and depends on the fortress of breeds, length of the shot or the well, type of substance and other conditions. During the carrying out pilot explosions without antidust actions dust content of air in 2 hours after explosion in driving excavations remains considerable. The most effective action at V. the ruble allowing to reduce the content of dust in air by 80 — 85% and to reduce time of airing by 2 — 2,5 times is use of tumanoobrazovatel and sprinklers. Considerably (more than by 20 times) dust content of air during the loading of the mountain weight humidified after explosion decreases.

The considerable effect of decrease in dust content of air at V. of river for the purpose of cutting of not dimension is reached by use of the paper vessels filled with water (Kraft). At the optimum relation of weight of water to the weight of a laid on charge 2: 1 dust content of air decreases by 10 — 14 times. As essential means of fight against dust at V. to river serves the internal water zaboyka applied generally in the form of the polyethylene ampoules filled with water placed in the shot or the well together with explosive substance. The water zaboyka reduces dust content of air by 2 — 3 times and interferes with adsorption of explosive gases on particles of dust.

The best conditions for purification of air after V. of river are provided at two shifts a day since at the same time during a long break between changes air is purified of products of explosion.

Especially high gigabyte. the effect gives a combination of ventilation, fogging, irrigation and other measures of fight against poisonous gases and dust at V.'s maintaining of river.

The Underground Nuclear Explosions (UNE) in the peace purposes — the explosions of nuclear devices conducted in the economic purposes. Structurally nuclear device consists of a container, in Krom automatic equipment of blasting and a nuclear charge is placed. Energy of explosion is emitted due to chain reaction of division of heavy-nuclei or synthetic reaction of easy kernels.

The technology of preparation and carrying out PYaV consists in the following. The nuclear device is placed at the set depth in the charging well or an adit. Lowering of the nuclear device to the well is made by means of drilling or other special rig on pipes, steel ropes or on a cable — a cable. For prevention of an exit of radioactive products of explosion to the Earth's surface the well (adit) is pressurized. Management of blasting and control of operability of a charge is exercised remotely from the command post (CP).

PYaV are subdivided on: explosions of outside action (excavation and incomplete camouflage); explosions are camouflage, not having the destroying effect on the Earth's surface and excluding emission of radioactive products of explosion in the atmosphere.

Explosions of outside action are applied: at construction of large hydraulic engineering constructions; for overburden works during the development of minerals; creations of trench dredging and embankments at construction iron and highways.

Camouflage explosions are applied: for an intensification of oil production and natural gas and elimination of emergency gas and oil fountains; creations of underground storage tanks — storages of industrial products and tanks for the purpose of burial of biologically harmful waste of the industry; by underground mining of ore fields; carrying out scientific research (e.g., in seismology).

The complex of actions is developed for elimination or decrease in possible effects from the seismic and radiation factors accompanying PYaV at design: choice of depth of laying of the nuclear device, optimum for these purposes; sealing of a trunk of the charging well (adit) and other developments entering a dangerous area of coverage of explosion; placement of the charging well at seismosafe distance from settlements and the industrial enterprises; ensuring seismic safety of local population and participants of works; the notification of authorities, local population and medical institutions about time of carrying out explosion; choice of favorable weather conditions; operating radiation control before carrying out explosion behind change of level of radioactivity.

Successful results of experimental and first trial PYaV give the grounds to assume that they can find broad application in the national economy.

PYaV in the peace purposes are carried out with respect for standards of radiation safety of NRB — 76 and the recommendations developed by the International commission on radiological protection (MKRZ) under close and constant control of bodies of State sanitary inspection of M3 of the USSR.


Bibliography: Atomic explosions in the peace purposes, under the editorship of I. D. Morokhov, M., 19 70; Izrael Yu. A. Peaceful nuclear explosions and environment, L., 197 4; Krivokhatsky A. S. and Katsapov V. I. Radiation safety at technical nuclear explosions, M., 1971, bibliogr.; Nifontov B. I., etc. Underground nuclear explosions, M., 1965, bibliogr.; Standards of radiation safety (NRB — 76), M., 19 76; The Main standards of safety at protection against radiation, Vienna IAEA, 1968; Heyfits S. Ya. and Baltaytis V. Ya. Labor protection and mine-rescue business, M., 1971; X at x r and N and E. V. and T to and the p e in V. V. Pneumoconiosis and their prevention, M.1968, bibliogr.; Peaceful nuclear exlosions, Vienna, IAEA, 1970—1975.

A. H. Marey, V. M. Mikhaylov, V. V. Tkachyov.

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