A rock bolt is a long
anchor bolt
Anchor bolts are used to connect structural and non-structural elements to concrete.. The connection can be made by a variety of different components: anchor bolts (also named fasteners), steel plates, or stiffeners. Anchor bolts transfer diffe ...
, for stabilizing rock excavations, which may be used in tunnels or rock cuts. It transfers load from the unstable exterior to the confined (and much stronger) interior of the rock mass.
Rock bolts were first used in mining in the 1890s, with systematic use documented at the St Joseph Lead Mine in the U.S. in the 1920s. Rock bolts were applied to civil tunneling support in the U.S. and in Australia starting in the late 1940s. Rock bolts were used and further developed starting in 1947 by Australian engineers who began experimenting with four-meter-long expanding anchor rock bolts while working on the
Snowy Mountains Scheme
The Snowy Mountains Scheme or Snowy scheme is a hydroelectricity and irrigation complex in south-east Australia. The Scheme consists of sixteen major dams; nine power stations; two pumping stations; and of tunnels, pipelines and aqueducts that ...
.
As shown in the figure, rock bolts are almost always installed in a pattern, the design of which depends on the
rock quality designation Core recovery parameters describe the quality of core recovered from a borehole.
Total core recovery
Total core recovery (TCR) is the borehole core recovery percentage.
TCR is defined as the quotient:
:TCR = \left(\frac\right)\times 100 %
:l_\ma ...
and the type of excavation. Rock bolts are an essential component of the
New Austrian Tunneling method
The New Austrian tunneling method (NATM), also known as the sequential excavation method (SEM) or sprayed concrete lining method (SCL), is a method of modern tunnel design and construction employing sophisticated monitoring to optimize various wa ...
. As with anchor bolts, there are many