volume with 2.7 billion kg of explosives consumed (13 m3 per capita), and Australia had the highest per capita explosives consumption that year with 45 m3 per capita. Procedure As the name suggests, drilling and blasting works as follows: A blast pattern is created A number of holes are drilled into the rock, which are then partially filled with explosives. Stemming, inert material, is packed into the holes to direct the explosive force into the surrounding rock. Detonating the explosive causes the rock to collapse. Rubble is removed and the new tunnel surface is reinforced. Repeating these steps until desired excavation is complete. The positions and depths of the holes (and the amount of explosive each hole receives) are determined by a carefully constructed pattern, which, together with the correct timing of the individual explosions, will guarantee that the tunnel will have an approximately circular cross-section. During operation, blasting mats may be used to contain the blast, suppress dust and noise, for fly rock prevention and sometimes to direct the blast. Rock support As a tunnel or excavation progresses the roof and side walls need to be supported to stop the rock falling into the excavation. The philosophy and methods for rock support vary widely but typical rock support systems can include: Rock bolts or rock dowels Shotcrete Ribs or mining arches and lagging Cable bolts In-situ concrete Typically a rock support system would include a number of these support methods, each intended to undertake a specific role in the rock support such as the combination of rock bolting and shotcrete. Gallery See also Building implosion Demolition International Society for Explosive Engineers References External links "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. This is an extensive survey of techniques used in the early 20th century. Tunnel construction Mining techniques Explosives Civil engineering