Civil Engineering Reference
In-Depth Information
Rock cut
stabilization and
protection
Stabilization
measures
Protection
measures
• Ditches
• Mesh
• Catch fences
• Warning
fences
• Rock sheds
• Tunnels
Reinforcement
Rock removal
• Resloping
• Trimming
• Scaling
• Rock bolting
• Dowels
• Tied-back walls
• Shotcrete
• Buttresses
• Drainage
• Shot-in-place
buttress
Figure 12.3
Categories or rock slope
stabilization measures.
construct a barrier. Therefore, alternative stabil-
ization measures may be to remove loose rock,
secure it in place with bolts, or to drape mesh
on the slope. It is generally preferable to remove
loose rock and eliminate the hazard, but only if
this will form a stable face and not undermine
other potentially loose rock on the face. If the
source of the rock falls is a zone of boulders in
an erodible soil matrix that cannot be stabilized
by bolting of effectively scaled, then a combin-
ation ditch-containment structure may be more
suitable. If there is limited space at the toe of the
slope for this work, there may be no alternative
but to relocate or realign the facility.
When selecting and designing stabilization
measures that are appropriate for a site, geotech-
nical, construction and environmental issues must
be considered. The geotechnical issues—geology,
rock strength, ground water, and stability
analysis—are discussed in previous chapters.
Construction and environmental issues, which
can affect the costs and schedule of the work,
must be addressed during the design phase of
the project. Issues that are frequently important
are equipment access, available work time during
traffic
closures,
and
disposal
of
waste
rock
and soil.
Another factor to consider in the selection
of stabilization measures is the optimum level
of work. For example, a minor scaling project
will remove the loosest rock on the slope face,
but, if the rock is susceptible to weathering, this
work may have to be repeated every three to
five years. Alternatively, a more comprehensive
program can be carried out using shotcrete and
bolting, in addition to scaling. Although the ini-
tial costs of this second program would be higher,
it would be effective for a longer period, per-
haps for 20-30 years. Alternative stabilization
programs such as these, including the alternative
of doing no work, can be compared using decision
analysis. Decision analysis is a systematic proced-
ure for evaluating alternative courses of action
taking into account the likely range of construc-
tion costs and design life of the stabilization work,
as well as the probability and costs of rock falls
occurring and causing accidents (Wyllie, 1980;
Roberds, 1991; Roberds
et al
., 2002).
