Civil Engineering Reference
In-Depth Information
and failure of landslides (Van Velsor and
Walkinshaw, 1991; Jibson and Harp, 1995).
Section 6.5 discusses methods to incorpor-
ate seismic ground motion in slope stability
analyses.
contrast, a reactive program places the emphasis
in areas where rock falls and accidents have
already occurred, and where the hazard may then
be diminished.
An effective proactive approach to stabiliza-
tion requires a consistent, long-term program
under the direction of a team experienced in
both the engineering and construction aspects of
this work. Another important component of this
work is to keep accurate records, with photo-
graphs, of slope conditions, rock falls and sta-
bilization work. This information will document
the location of hazardous areas and determine the
long-term effectiveness of the program in redu-
cing the incidence of rock falls. These records can
be most conveniently handled using database pro-
grams that readily allow updating and retrieval of
records.
12.3 Rock slope stabilization programs
On transportation systems in mountainous ter-
rain, there may be hundreds of rock slopes
with a variety of rock fall hazards resulting in
a significant cost to the operator. Under these
circumstances, a long-term, multi-year stabil-
ization program is often justified; this section
describes the steps involved in implementing such
a program.
12.3.1 Planning stabilization programs
12.3.2 Rock slope inventory systems
When implementing a program to stabilize a large
number of slopes, the best use of available funds
is often made by setting up a systematic program
that identifies and rates the most hazardous sites.
Annual stabilization work can then be scheduled,
with the most hazardous sites having the highest
priority. Table 12.2 shows an example of how
such a program may be structured.
The objective of the program shown in
Table 12.2 is to be proactive in identifying and
stabilizing slopes before rock falls and accidents
occur. This requires a careful examination of each
site to identify the potential hazard, and estim-
ate the likely benefit of the stabilization work. In
The relative rock fall hazard at a site as compared
to other sites can be used in selecting priorities.
Early work on this topic by Brawner and Wyllie
(1975) and Wyllie (1987), was adapted by Pierson
et al
. (1990) into a process for the rational man-
agement of rock slopes on highways, which has
been named the Rock Fall Hazard Rating System
(RHRS). The first step in this process is to make an
inventory of the stability conditions of each slope
so that they can be ranked according to their rock
fall hazard (Steps 1 and 2 in Table 12.2).
The rock fall areas identified in the inventory
are ranked by scoring the categories shown in
Table 12.2
Rock slope stabilization for transportation systems
Step 1
Prepare
inventory of
rock slopes
with hazard
rating assigned
to each slope
and organize
records in
database.
Step 2
Rank slopes
according to
hazard
rating to
identify the
highest priority
locations.
Step 3
Select a
number of the
highest priority
locations for
inclusion in
annual
stabilization
program.
Step 4
Determine
most
appropriate
stabilization
measure(s) for
each site, and
prepare
designs and
specifications.
Step 5
Carry out
stabilization
work possible
using time and
material
contract that
can
accommodate
changing
conditions that
develop during
the work.
Step 6
Update
database with
rock fall and
stabilization
records.
Step 7
Reassess
hazard ratings,
and return to
Step 3 to select
sites for
subsequent
years
stabilization
work.
