6
per size for statistical runout analysis. At this time, the
Highwall Safety project team has developed and purchased
enough rock molds to make an entire suite of rocks per
concrete pour. One suite of rocks is used per rockfall test
trip to a collaborating mine site. One rockfall testing trip
takes a week, which includes final scouting and sites train-
ing, at least two single bench rockfall tests, and a full high-
wall test to finish. Each rockfall test takes a full day for set
up, testing, clean-up, and loading of rocks to take to the
next testing location. The highwall test is purposely left as
the final rockfall test for the week due to the rocks being
unretrievable, which also explains why one suite of rocks
is used per trip. Moving forward, NIOSH researchers are
working with concrete mixing/pouring companies local to
collaborating mine sites to develop suites of synthetic rocks
using the already developed molds to reduce travel time
with heavy loads from Spokane, WA.
Another lesson was learned with regards to data acqui-
sition prior to testing. While there are times where ideal
rock drop locations are limited for full highwall rockfall
tests due to accessibility, the NIOSH research team learned
that it is important to get a drone photogrammetry model
developed of each testing location for analysis before each
test occurs to ensure the drop point is as realistic to min-
ing conditions as possible. For example, there was a case
where a highwall with 6 benches of double 40-foot bench
height to the pit bottom was chosen for rockfall testing.
A drop point was chosen without acquiring a drone pho-
togrammetry model and testing commenced. It was later
discovered that the first bench was a single 40-foot height
with the remaining benches being double 40 foot, causing
inconsistency in bench catchment from the very start. This
is shown in Figure 4.
Additionally, it was discovered that the second bench
had a slight berm which increased catchment potential
early in the rock’s path of travel. Factors such as these need
to be analyzed prior to rockfall testing to ensure that the
chosen drop point provides the most useful data for col-
laborating mine sites.
During Rockfall Testing
In the early stages of the rockfall testing program, all rock
sizes and shapes were sent down the bench or highwall,
either a pallet at a time or by bucket load, until testing
was completed, and a single drone flight was acquired to
develop a photogrammetry model and to measure/identify
where all the rocks had traveled. It was quickly discovered
that this caused issues in identification of rocks 6 inches and
smaller in diameter due to being buried or destroyed by the
larger synthetic/local rocks. Additionally, the final resting
place of some rocks altered or even completely stopped the
path of travel of others. To fix both issues for single bench
testing scenarios, a methodology was developed where each
size of rocks was sent down the slope as individual sets. For
each set, a drone flight was acquired after all the rocks of
that specific size category were dropped, and then the rocks
were cleared before dropping the next size set. This meth-
odology cannot be applied in full highwall testing scenarios
because the rocks cannot be cleared between size sets due to
inaccessibility on benches below the drop point. Therefore,
for highwall testing scenarios, the rocks are dropped from
the largest size (18-inch diameter) to smallest size (3-inch
diameter) as the larger sizes typically travel farther and
would not hinder the travel path or destroy/cover up the
smaller rock sizes.
Another lesson was learned with regards to initial veloc-
ity of the rocks from the drop point. Prior to the Highwall
Safety project team owning the Genie telehandler, rocks
were dropped from a bucket on an excavator or other piece
of loading equipment, which typically gave them a larger
rotational velocity than desired. Once the Genie telehan-
dler with the fork attachment was acquired, a new meth-
odology was developed in which the synthetic rocks, sizes
6-inch diameter and larger, would be loaded on a pallet,
placed on flat ground at the drop point, and slowly pushed
off the pallet using another pallet on the forks of the tele-
handler. For all the local rocks and synthetic rocks sized
3 inch in diameter, they were similarly loaded on a pallet
and placed at the drop point but then manually pushed
individually using a 6-foot steel rod with a plate on the end.
This all allowed for the least initial velocity possible to best
simulate a natural rockfall scenario. Figure 4. Photogrammetry model of sample highwall test
showing single 40-foot bench followed by remaining double
40-foot benches.
per size for statistical runout analysis. At this time, the
Highwall Safety project team has developed and purchased
enough rock molds to make an entire suite of rocks per
concrete pour. One suite of rocks is used per rockfall test
trip to a collaborating mine site. One rockfall testing trip
takes a week, which includes final scouting and sites train-
ing, at least two single bench rockfall tests, and a full high-
wall test to finish. Each rockfall test takes a full day for set
up, testing, clean-up, and loading of rocks to take to the
next testing location. The highwall test is purposely left as
the final rockfall test for the week due to the rocks being
unretrievable, which also explains why one suite of rocks
is used per trip. Moving forward, NIOSH researchers are
working with concrete mixing/pouring companies local to
collaborating mine sites to develop suites of synthetic rocks
using the already developed molds to reduce travel time
with heavy loads from Spokane, WA.
Another lesson was learned with regards to data acqui-
sition prior to testing. While there are times where ideal
rock drop locations are limited for full highwall rockfall
tests due to accessibility, the NIOSH research team learned
that it is important to get a drone photogrammetry model
developed of each testing location for analysis before each
test occurs to ensure the drop point is as realistic to min-
ing conditions as possible. For example, there was a case
where a highwall with 6 benches of double 40-foot bench
height to the pit bottom was chosen for rockfall testing.
A drop point was chosen without acquiring a drone pho-
togrammetry model and testing commenced. It was later
discovered that the first bench was a single 40-foot height
with the remaining benches being double 40 foot, causing
inconsistency in bench catchment from the very start. This
is shown in Figure 4.
Additionally, it was discovered that the second bench
had a slight berm which increased catchment potential
early in the rock’s path of travel. Factors such as these need
to be analyzed prior to rockfall testing to ensure that the
chosen drop point provides the most useful data for col-
laborating mine sites.
During Rockfall Testing
In the early stages of the rockfall testing program, all rock
sizes and shapes were sent down the bench or highwall,
either a pallet at a time or by bucket load, until testing
was completed, and a single drone flight was acquired to
develop a photogrammetry model and to measure/identify
where all the rocks had traveled. It was quickly discovered
that this caused issues in identification of rocks 6 inches and
smaller in diameter due to being buried or destroyed by the
larger synthetic/local rocks. Additionally, the final resting
place of some rocks altered or even completely stopped the
path of travel of others. To fix both issues for single bench
testing scenarios, a methodology was developed where each
size of rocks was sent down the slope as individual sets. For
each set, a drone flight was acquired after all the rocks of
that specific size category were dropped, and then the rocks
were cleared before dropping the next size set. This meth-
odology cannot be applied in full highwall testing scenarios
because the rocks cannot be cleared between size sets due to
inaccessibility on benches below the drop point. Therefore,
for highwall testing scenarios, the rocks are dropped from
the largest size (18-inch diameter) to smallest size (3-inch
diameter) as the larger sizes typically travel farther and
would not hinder the travel path or destroy/cover up the
smaller rock sizes.
Another lesson was learned with regards to initial veloc-
ity of the rocks from the drop point. Prior to the Highwall
Safety project team owning the Genie telehandler, rocks
were dropped from a bucket on an excavator or other piece
of loading equipment, which typically gave them a larger
rotational velocity than desired. Once the Genie telehan-
dler with the fork attachment was acquired, a new meth-
odology was developed in which the synthetic rocks, sizes
6-inch diameter and larger, would be loaded on a pallet,
placed on flat ground at the drop point, and slowly pushed
off the pallet using another pallet on the forks of the tele-
handler. For all the local rocks and synthetic rocks sized
3 inch in diameter, they were similarly loaded on a pallet
and placed at the drop point but then manually pushed
individually using a 6-foot steel rod with a plate on the end.
This all allowed for the least initial velocity possible to best
simulate a natural rockfall scenario. Figure 4. Photogrammetry model of sample highwall test
showing single 40-foot bench followed by remaining double
40-foot benches.