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Rockfall
protection
Rockfall protection is necessary wherever people or equipment
may be located at the base of a rock face. This is a serious
issue because the majority of people who are killed or seriously
injured as a result of rockfalls are affected by small rather
than large pieces of rock.
There are a variety of measures that can be used, including:
- Rock traps in the form of ditch and barrier type structures.
Often the barrier is simply a low bank of waste rock or
soil.
- Placing waste rock against a face, known as slope buttressing
(although the stability of the waste rock also needs to
be considered).
- Surface protection such as spray concrete, netting, rock
bolts or other anchors.
- Face scaling, ie the controlled removal of loose rock
- Intermediate benching, ie the formation of ledges across
the face.
- Pre-split blasting, ie a method of blasting which results
in a less broken surface to the rock face. However this
does not overcome any underlying stability problems, such
as weak layers, within the face and it can be unsightly.
In some circumstances the rock face itself may be of geological
importance (it may be a geological SSSI) and therefore should
not be obscured. This will prevent the use of some surface
protection measures, such as netting or spray concrete, and
alternatives will need to be considered. A compromise may be
reached by using netting above the key location, for example,
while leaving the important part open.
 Partial
slope buttressing using tipped material. |
 Netting
on unconsolidated slope to protect against erosion.
Pre-split blasting to reduce rockfall.
As many kilometres of rock face may be involved, both during
the life of the quarry and as part of its restoration, simple
measures are often the most suitable to ensure safety at a
reasonable cost.
The simpler alternatives to surface protection measures include
face scaling, which involves the controlled removal of loose
and hazardous materials in a safe manner to achieve a more
solid rock face, and rock traps. Face scaling will need to
be repeated regularly as weathering will continue to loosen
pieces.
Rock traps are frequently used at the base of rock faces in
active quarries, particularly above access roads where there
is a risk of rockfall onto vehicles. It is important to ensure
that a ditch and barrier type structure is of sufficient size,
in both height and width, to avoid rocks bouncing over them.
Debris collected in the ditch must be regularly removed.
 Sketch
of rock traps showing a ditch and mound at the base of the
slope and tipped material on the bench. |
