5
One of the key features that the radar unit offered was
the ability to see small, but potentially important changes
or shifts in the high-wall movement. Utilizing the charts
in the software, the Geotechnical Department could see in
real-time increases in average velocity, and velocity delta,
and monitor any changes to the relative range (distance
from the slope to the radar unit). Due to the extreme sen-
sitivity of the high walls to any increased precipitation
and mining activities within the pit, the Geotechnical
Department quickly adopted a protocol that relied heavily
on interpreting the small changes seen in the radar data.
With near-constant movement, the velocity delta chart
proved to be the most reliable way to predict when the
moving mass was changing into a progressive failure. Tight
alarm thresholds were placed around the velocity delta, and
strict protocols for those working in the area were devel-
oped. This included cessation of mining activities, removal
of equipment and personnel from the area, or the closure of
the haul road into the pit should alarms be received.
Observational Methods
The ongoing and dynamic nature of the slope move-
ments experienced in this pit meant that a more hands-
on approach to slope monitoring was required throughout
the pit mining operations. In-field assessments were cru-
cial to understanding the wall performance and keeping
personnel safe.
The Geotechnical Department of the mine routinely
performed visual inspections of all areas of movement
within the pit, as well as the condition of the haul road.
Any changes found were noted and shared with the rest
of the engineering team as well as Mine Operations. New
tension cracks were painted bright orange, and GPS coor-
dinates were taken to mark their location. Pieces of lathe
were often used as makeshift extensometers to help gauge
tension crack growth.
The Pit Supervisors were also encouraged to report any
changes they observed in the high-walls or haul road dur-
ing their shift to the Geotechnical Department. When a
report or concern was received, the area involved was visu-
ally inspected by a Geotechnical Engineer. If the area was
not able to be inspected due to weather, or darkness, the
area was bermed off and the inspection occurred as soon
as it was daylight or the weather cleared. Mining activities
could be halted even without an active radar alarm.
Effective communication and building trust with the
Mine Operations department was key in successfully using
the observational method. The Geotechnical Group ben-
efited from the additional ‘eyes on the wall’ that the Pit
Supervisors provided. In turn, the Pit
Supervisors understood that the Geotechnical
Department would take their concerns seriously to keep
their personnel safe.
CREATIVE MINING
Traditional mine planning and removal techniques were
not effective in an open pit that had such active and chang-
ing high walls. This forced the mine to adopt creative min-
ing methods to both manage the high walls and provide a
safe and productive working environment.
Both the mine planners and pit operators had to be
open and flexible to frequent mine design changes and had
to be comfortable making ‘on the fly’ and ‘field fit’ deci-
sions to avoid equipment idling and to keep the progres-
sion of the pit on track to forecast.
North Haul Ramp Maintenance
Due to pit geometry and ore body restrictions, the only
viable access into the pit had to cross the northern wall
instability. This meant that safe access had to be maintained
despite the road being subjected to average daily velocities
that ranged from 2 to 33 inches per day.
Initially, maintenance of the haul road only required
tension cracks or soft spots to be repaired weekly, or bi-
weekly. Repairing the cracks involved a dozer or grader rip-
ping the ground as deep as possible, and then blading over
the area. This not only provided a smoother running sur-
face but also sealed the cracks from channeling any surface
water into the failure mass.
As mining progressed in the pit, the average velocity
increased on the haul road. This caused the road to slump
and become steeper than originally designed. When the
road became too steep for haul traffic, additional material
was dumped in, and the road was rebuilt back to a 10 per-
cent ramp.
Eventually, this method became ineffective as well.
During the life of the pit, the entire haul road was dozed
down to an angle of repose that matched the high-wall,
and additional material was brought in to completely
rebuild the section of road that crossed the failing mass sev-
eral times. Each time this mitigation was performed, the
haul road would have a limited time before it was neces-
sary to repeat. Towards the end of the pit, major dozing
activities were occurring on the road every day to maintain
safe access.
Before each mitigation was performed on the haul
road, data from the radar unit was analyzed to determine if
the high wall was indicating a progressive failure mode. The
radar data was also closely watched during each mitigation
One of the key features that the radar unit offered was
the ability to see small, but potentially important changes
or shifts in the high-wall movement. Utilizing the charts
in the software, the Geotechnical Department could see in
real-time increases in average velocity, and velocity delta,
and monitor any changes to the relative range (distance
from the slope to the radar unit). Due to the extreme sen-
sitivity of the high walls to any increased precipitation
and mining activities within the pit, the Geotechnical
Department quickly adopted a protocol that relied heavily
on interpreting the small changes seen in the radar data.
With near-constant movement, the velocity delta chart
proved to be the most reliable way to predict when the
moving mass was changing into a progressive failure. Tight
alarm thresholds were placed around the velocity delta, and
strict protocols for those working in the area were devel-
oped. This included cessation of mining activities, removal
of equipment and personnel from the area, or the closure of
the haul road into the pit should alarms be received.
Observational Methods
The ongoing and dynamic nature of the slope move-
ments experienced in this pit meant that a more hands-
on approach to slope monitoring was required throughout
the pit mining operations. In-field assessments were cru-
cial to understanding the wall performance and keeping
personnel safe.
The Geotechnical Department of the mine routinely
performed visual inspections of all areas of movement
within the pit, as well as the condition of the haul road.
Any changes found were noted and shared with the rest
of the engineering team as well as Mine Operations. New
tension cracks were painted bright orange, and GPS coor-
dinates were taken to mark their location. Pieces of lathe
were often used as makeshift extensometers to help gauge
tension crack growth.
The Pit Supervisors were also encouraged to report any
changes they observed in the high-walls or haul road dur-
ing their shift to the Geotechnical Department. When a
report or concern was received, the area involved was visu-
ally inspected by a Geotechnical Engineer. If the area was
not able to be inspected due to weather, or darkness, the
area was bermed off and the inspection occurred as soon
as it was daylight or the weather cleared. Mining activities
could be halted even without an active radar alarm.
Effective communication and building trust with the
Mine Operations department was key in successfully using
the observational method. The Geotechnical Group ben-
efited from the additional ‘eyes on the wall’ that the Pit
Supervisors provided. In turn, the Pit
Supervisors understood that the Geotechnical
Department would take their concerns seriously to keep
their personnel safe.
CREATIVE MINING
Traditional mine planning and removal techniques were
not effective in an open pit that had such active and chang-
ing high walls. This forced the mine to adopt creative min-
ing methods to both manage the high walls and provide a
safe and productive working environment.
Both the mine planners and pit operators had to be
open and flexible to frequent mine design changes and had
to be comfortable making ‘on the fly’ and ‘field fit’ deci-
sions to avoid equipment idling and to keep the progres-
sion of the pit on track to forecast.
North Haul Ramp Maintenance
Due to pit geometry and ore body restrictions, the only
viable access into the pit had to cross the northern wall
instability. This meant that safe access had to be maintained
despite the road being subjected to average daily velocities
that ranged from 2 to 33 inches per day.
Initially, maintenance of the haul road only required
tension cracks or soft spots to be repaired weekly, or bi-
weekly. Repairing the cracks involved a dozer or grader rip-
ping the ground as deep as possible, and then blading over
the area. This not only provided a smoother running sur-
face but also sealed the cracks from channeling any surface
water into the failure mass.
As mining progressed in the pit, the average velocity
increased on the haul road. This caused the road to slump
and become steeper than originally designed. When the
road became too steep for haul traffic, additional material
was dumped in, and the road was rebuilt back to a 10 per-
cent ramp.
Eventually, this method became ineffective as well.
During the life of the pit, the entire haul road was dozed
down to an angle of repose that matched the high-wall,
and additional material was brought in to completely
rebuild the section of road that crossed the failing mass sev-
eral times. Each time this mitigation was performed, the
haul road would have a limited time before it was neces-
sary to repeat. Towards the end of the pit, major dozing
activities were occurring on the road every day to maintain
safe access.
Before each mitigation was performed on the haul
road, data from the radar unit was analyzed to determine if
the high wall was indicating a progressive failure mode. The
radar data was also closely watched during each mitigation