Rock blasting

Rock blasting in Finland

Rock blasting is the controlled use of explosives and other methods such as gas pressure blasting pyrotechnics or plasma processes, to excavate, break down or remove rock. It is practiced most often in mining, quarrying and civil engineering such as dam or road construction. Except in mining, the result of rock blasting is often known as a rock cut.

The use of explosives in mining goes back to the year 1627,^[1] when gunpowder was first used in place of mechanical tools in the Hungarian (now Slovakian) town of Banská Štiavnica. The innovation spread quickly throughout Europe and the Americas.

Rock blasting currently utilizes many different varieties of explosives with different compositions and performance properties. Higher velocity explosives are used for relatively hard rock in order to shatter and break the rock, while low velocity explosives are used in soft rocks to generate more gas pressure and a greater heaving effect. For instance, an early 20th-century blasting manual compared the effects of black powder to that of a wedge, and dynamite to that of a hammer.^[2] The most commonly used explosives in mining today are ANFO based blends due to lower cost than dynamite.

In 1990, 2.1 million tonnes (2.32 million short tons) of commercial explosives were consumed in the USA, representing an estimated expenditure of 3.5 to 4 billion 1993 dollars on blasting. Australia had the highest explosives consumption that year at 500 million tonnes (551 million short tons), with Scandinavian countries another leader in rock blasting (Persson et al. 1994:1).

The potential of nuclear explosives for rock blasting and earth-moving was tested by the United States and Soviet Union in the 1960s and 70s as the focus of two research projects, Operation Plowshare and Nuclear Explosions for the National Economy respectively. Their potential was never used beyond mere experimentation, due to ensuing issues of radioactivity and public opposition, and was ended alongside the general end of atmospheric testing of nuclear explosives.

Gallery

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  Blast hole drilling with Tamrock Scout 700

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  Blast-hole drilling at the Bingham Canyon Mine, Utah. Note the pattern of drill holes being prepared for blasting.

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  Loading blast holes with ANFO

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  Rock surface newly blasted. This is called pre-split, it's a technique to leave a smooth face.

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  Sideling Hill road cut formed by rock blasting

See also

• Demolition
• Building implosion
• Plasma blasting

Notes

References

• Persson, Per-Anders; Roger Holmberg; Jaimin Lee (1994). Rock Blasting and Explosives Engineering. Boca Raton, Fla.: CRC Press. ISBN 0-8493-8978-X. 

External links

Wikimedia Commons has media related to Rock blasting.

• "Air Curtain Fences Blast" Popular Mechanics, August 1954, pp. 96–97, the delicate controlled blast in 1954 to connect the two reservoirs at a Canadian Niagara Falls power station.
•  Charles L. Hogeboom (1879). "Blasting". The American Cyclopædia. 

•  "Blasting". Encyclopædia Britannica 4 (11th ed.). 1911. pp. 44–48.  This is an extensive survey of techniques used in the early 20th century.