Rock bolting is one of the most efficient supporting devices ever developed. The earliest case of using bolts as a rock reinforcement method was in a slate quarry in North Wales in 1872 (Schach et al., 1979). In 1918 a coal mine in Germany introduced bolts as a means of ground reinforcement (Lang et al. 1979). Mechanical rockbolts were applied in a metal mine in the United States in 1927 (Bolstad and Hill, 1983). The U.S Bureau of Mines (USBM) attempted to carry out early studies on the fundamental mechanism of bolting techniques and apply the roof bolting system to maintain roof strata stability in 1947. In less than two years, rockbolting system spreads widely throughout the U.S. and more than 200 coal mines employed this new roof method. By 1952, annual consumption of roof bolts was 25 million (Jalalifar, 2006). Un-tensioned fully encapsulated rockbolts were initially used in poor ground in the early seventies. In the 1980s, fully encapsulated bolts accounted for approximately half the bolt consumption in the United States coal mines. In 1988 the total bolt consumption within the United States underground mines rose to 85 million, of which 40% were mechanical and 39% were resin rebar bolts. In 1991, the bolt consumption in U.S. underground mines increased to 115 million, of which mechanical bolts accounted for 34% and resin rebar bolts were 53% (Hillyer, 2012). In 2006, the number of bolts installed within United States decreased to 68 million, with resin rebar bolts making up 80% (Peng, 2008). The declining use of rockbolts was attributed to the greatly increasing production by longwall mining, which used a quarter of the roof bolt consumption of continuous mining.
History of Rock Bolting
Australia began the use of rockbolts in Elrington Colliery, New South Wales in 1949. Rockbolts have grown to be the prominent reinforcing approach in most underground coal mines in Australia since 1983. Australia mining industry consumes about seven million bolts every year (Cao, 2012). Currently, the rockbolting system is accepted to be much more effective than timbers and steel girders and is quick and easy to install. There are about 15,000 km of bolted mine roadways developed in US coal mines per year. In 2011, the rockbolt usage of USA, Australia and the whole world are 95, 7 and 500 million respectively (Hillyer, 2012).