1
24-024
Designing a Rockfall Testing Program for Open-Pit Mines to
Investigate Runout and Bench Catchment
Josef Bourgeois
CDC/NIOSH/SMRD, Spokane, WA
Sean Warren
CDC/NIOSH/SMRD, Spokane, WA
ABSTRACT
The potential of rockfall at open-pit mines presents a con-
tinuous hazard to mine workers and is typically mitigated by
designing catch benches at empirically determined widths.
The National Institute for Occupational Safety and Health
(NIOSH) is working in conjunction with industry and aca-
demia to revisit and update current catch bench guidelines
to better match acceptable risk tolerances for modern min-
ing practices. To begin this process, a rockfall testing pro-
gram was designed to gather empirical runout and bench
catchment data at partnering mine sites in the Western
United States. This paper presents a detailed description of
each component of the rockfall testing program, including
scouting and safety plan development, equipment require-
ments, synthetic rock development for uniform testing
across varying bench configurations, local rock collection
for testing of mine-specific geology, data acquisition dur-
ing testing, and data processing. Additionally, this paper
describes how the program has been updated over time
according to lessons learned during initial rockfall testing.
INTRODUCTION
Rockfall can occur in open-pit mines due to slope degra-
dation and can be made more severe through inadequate
implementation of slope design. The dynamics of these
events are largely a function of the mechanical proper-
ties of the detached rock, location of the detachment, the
rock mass, and downslope profile [1]. Rockfall potential
is one of the most significant geotechnical hazards to the
open-pit mining workforce [2] and is typically addressed by
catch benches as required by the Mine Safety and Health
Administration (MSHA). The Modified Ritchie Criterion
(MRC) is an industry-accepted standard in North and
South America for initial rockfall catch bench design [3]
and is presented in Equation 1 [4].
W =0.2H +4.5 (1)
where:
W =minimum catch bench width (m)
H =bench height (m)
While the MRC only considers bench height in calcu-
lating minimum catch bench width, individual mine stud-
ies [5] [6] [7] show that rockfall hazard and catch bench
performance are a function of multiple variables, includ-
ing bench face angle, rock size/shape (geology), operational
practices (e.g. blasting), and bench berms. Williams et
al. [8] state that, although efforts to understand rockfall
behavior in relation to bench design have been completed,
each individual mine site possesses its own specific set of
constraints and conditions, thus requiring custom investi-
gation. Statistical analysis programs, such as RocFall [9],
can be used to assist with the assessment of slopes at risk for
rockfall events.
24-024
Designing a Rockfall Testing Program for Open-Pit Mines to
Investigate Runout and Bench Catchment
Josef Bourgeois
CDC/NIOSH/SMRD, Spokane, WA
Sean Warren
CDC/NIOSH/SMRD, Spokane, WA
ABSTRACT
The potential of rockfall at open-pit mines presents a con-
tinuous hazard to mine workers and is typically mitigated by
designing catch benches at empirically determined widths.
The National Institute for Occupational Safety and Health
(NIOSH) is working in conjunction with industry and aca-
demia to revisit and update current catch bench guidelines
to better match acceptable risk tolerances for modern min-
ing practices. To begin this process, a rockfall testing pro-
gram was designed to gather empirical runout and bench
catchment data at partnering mine sites in the Western
United States. This paper presents a detailed description of
each component of the rockfall testing program, including
scouting and safety plan development, equipment require-
ments, synthetic rock development for uniform testing
across varying bench configurations, local rock collection
for testing of mine-specific geology, data acquisition dur-
ing testing, and data processing. Additionally, this paper
describes how the program has been updated over time
according to lessons learned during initial rockfall testing.
INTRODUCTION
Rockfall can occur in open-pit mines due to slope degra-
dation and can be made more severe through inadequate
implementation of slope design. The dynamics of these
events are largely a function of the mechanical proper-
ties of the detached rock, location of the detachment, the
rock mass, and downslope profile [1]. Rockfall potential
is one of the most significant geotechnical hazards to the
open-pit mining workforce [2] and is typically addressed by
catch benches as required by the Mine Safety and Health
Administration (MSHA). The Modified Ritchie Criterion
(MRC) is an industry-accepted standard in North and
South America for initial rockfall catch bench design [3]
and is presented in Equation 1 [4].
W =0.2H +4.5 (1)
where:
W =minimum catch bench width (m)
H =bench height (m)
While the MRC only considers bench height in calcu-
lating minimum catch bench width, individual mine stud-
ies [5] [6] [7] show that rockfall hazard and catch bench
performance are a function of multiple variables, includ-
ing bench face angle, rock size/shape (geology), operational
practices (e.g. blasting), and bench berms. Williams et
al. [8] state that, although efforts to understand rockfall
behavior in relation to bench design have been completed,
each individual mine site possesses its own specific set of
constraints and conditions, thus requiring custom investi-
gation. Statistical analysis programs, such as RocFall [9],
can be used to assist with the assessment of slopes at risk for
rockfall events.